Initially born in China, Weilan was born and raised into the Eastern Pod. Her grandmother was on the Mermaid Council and she introduced her to Nerissa. Aurora set her sights on the Eastern Pod and a battle ensued between Aurora and the Eastern Pod for years. She was forced to move onto land with her grandmother when a Water Dragon wiped out the entire Eastern pod. Ever since the encounter of the Dragon, Weilan has been wary of living in the sea and prefers to live on land.
One night, Weilan encountered the Dragon and her grandmother sent her away for safe keeping. She went to the Gold Coast in Australia and is welcomed by Rita who she and her grandmother had met before when Rita visited China. Rita introduced her to Ondina and Mimmi. Although, Mimmi did everything she can to make her feel welcomed and show her around Rita's house and grotto, the infamous Mako Island Moon Pool, and Ocean Cafe, Ondina took an immediate disliking to her. Mostly out of jealousy for saving her student, being so different from what Ondina thinks is a real mermaid, her dry sense of humor that makes her seem hard to please, and the mystery of why she did not have a pod.
As Mimmi prepared to introduce Weilan to her friends, Weilan was surprised to learn that there were land people who knew the existence of mermaids such as Cam, Carly, David, and Evie, who was also part-mermaid at the time. She was even more stunned when she learns that Mimmi's brother Zac is a merman and immediately expresses interest in meeting him. Upon being introduced to Zac, she showed him no hardship despite the previous history between mermaids and mermen. When Ondina, Mimmi, and Evie leave for the pod's Full Moon Ceremony, Weilan remains behind, due to not having a moon ring.
However, Zac suddenly had a vision of a water dragon face-to-face with Mimmi. Weilan was horrified upon hearing the mermaids' endangerment, so she follows Zac as they rush to Mako. Weilan warns the group that the dragon is harmless to land people but according to past experience the Water Dragon is destructible to mermaids. It wiped out her pod and believes that no mermaid can stop and moon rings are useless against it.
Following this, tension between Ondina and Weilan only grows as she blames her for bringing the dragon to the pod. Weilan tries to be patient with her and suggest they make a fresh start, but Ondina is not interested. She even goes so far as to insult her by accusing her of not being a real mermaid, greatly angering and offending her. Weilan later finds the companionship she seeks in Zac, who also grew up on land even though he was born in the sea and got off to a bad start with Ondina. The two of them quickly become very good friends and later classmates when Weilan enrolls at Zac and Evie's school.
Weilan and Ondina also begin to become friends after Weilan saves Ondina from being exposed by workers at the marine park who were investigating the moon pool. However, they are not above wise cracking each other when the opportunity presents itself. Their respect for one another would grow more in "New Beginnings" when Ondina's moon ring lessons with Evie goes awry and cause her to be stuck floating in midair, much to Weilan's amusement. She attempts to pull her down only to fall into the same spell and they are left on their own when a panicked Evie leaves them to find Mimmi. The two of them are able to work together to restore themselves to the ground and admit to the other that they are not so bad.
As the mermaids prepare for the dragon, Weilan is increasingly bothered by Veridia's confidence that they can destroy the dragon with their moon rings despite her warnings of what took place in the eastern pod. She also displays knowledge of powerful magic that originates from the eastern pod including a technique called "Turn the Tide" that causes any magic to be redirected back to where it came from. When Zac learns of this technique, he begs Weilan to teach it to him in the hopes of using it to turn the dragon's power back on itself. Weilan is reluctant at first since it took years for the mermaids of the eastern pod to master it and they were still unable to defeat the dragon.
She is eventually convinced however when Zac makes the strong point that he is a merman and may have a better chance of defeating it. Both of them also agree that the others, especially Evie and Mimmi, cannot know what they are doing for they would surely see Zac's role in their plan as suicide on his part and would do everything they could to stop him. Weilan proves to be a very stern teacher and the lessons prove much more difficult then Zac thought and he almost considers giving up. However, after many practice attempts and forcing Zac's hand by attacking him while cloaked, he is successfully able to execute and master the technique much to both of their joy.
The two engage in a celebratory hug that is seen by Evie and she mistakenly assumes Zac is cheating on her. Although Zac is able to clear the misunderstanding, he does not reveal his and Weilan's plan. Afterwards, Weilan warns Zac that although his efforts to master Turn the Tide worked, it does not guarantee he will succeed against the dragon which he fully accepts.
When the day before the full moon comes, Weilan and Zac make the final preparations to put their plan into action. She informs Zac that the dragon will appear in the east where the moon rises and instructs him to lure the dragon to the moon pool to prevent it from escaping when he turns the dragon's own cold fire breath back at it. Zac then arranges a date with Evie at his place and has Cam to keep an eye on her and cover for Zac by claiming he will just be a little late. Meanwhile, Weilan makes certain the pod stays out of the way by manipulating Veridia into having the pod hide on the west side of the island under the guise that they will be able to attack the dragon under the element of surprise. Unfortunately, Zac's plan to keep Evie occupied hits a blow when Evie decides that she must help the pod fight the dragon and comes with the exact same plan Zac does to prevent him from trying to stop her by having Carly cover for her.
As Weilan sees Zac off before his fight with the dragon, Evie spots them. Realizing something is wrong, Evie confronts Weilan on what they have been up to the past couple of days. Weilan tries to get Evie to drop it, but she does not let up and she reveals what Zac is planning to do believing it is too late for her to interfere now. However, Evie successfully deduces that Zac is going to the moon pool and races after him despite Weilan's pleas. In the aftermath of it all, Weilan and Zac's plan ends in total failure and Evie loses her tail in the process.
Weilan is harshly scolded by Ondina and she considers leaving the Gold Coast for good, deeply ashamed for what she has done. She later runs into a antic dealer she had met previously named Uncle Shen who attempts to offer her comfort and convince that running away from her problems will not solve them. In spite of this, still considers running away hoping the dragon will follow her but Ondina realizes she was too harsh and that Weilan truly was trying to help. The two then make up and their developing friendship is restored. Weilan then apologizes to Evie, who decides to reap the benefits of being an ordinary girl again and the group makes up.
As the season progresses, Weilan gradually begins to embrace her mermaid roots once again. During the second half of season 3, Weilan and the rest of the group continue to search for a way to defeat the Dragon. Later, Weilan is stunned to learn that Zac and Mimmi are the children of the legendary Nerissa as they begin to share visions of a mermaid who Mimmi believes is her. Weilan then reveals that she had the chance to meet Nerissa once and she and the rest of the eastern pod idolized her. She also revealed that Nerissa came to their rescue when the eastern pod was attacked by a rebel mermaid named Aurora and that Nerissa disappeared after leaving to confront her.
Close to the season climax, the mermaids find a potential solution to defeat the dragon. While attending a book signing of a world famous treasure hunter named Rikki Chadwick, they notice a dragon bracelet that is associated with an ancient Chinese legend known as the Jao Long Dragon. After examining a picture of the Jao Long Dragon from Uncle Shen, Weilan notices a mermaid using the same bracelet against the dragon. Believing it can slay the dragon, the mermaids ask Riki for the bracelet, but she turns them away. The girls then enlist Zac's help to steal it, but the heist is ultimately unsuccessful. The mermaid council then make a plan B to destroy the dragon by unleashing the full power of Mako. Later, while paying a visit to Uncle Shen, Weilan learns an important detail regarding the legend from Uncle Shen. The bracelet did not kill the Jao Long dragon, but broke a spell that a land boy was placed under that turned him into the dragon by a another pod of mermaids as punishment for falling in love with a Chinese mermaid.
Weilan then concludes that Nerissa may be under the same kind of spell. She and Ondina then make another attempt to get the bracelet. After finding Riki in the moon pool, they are eventually able to convince her to give them the bracelet. As the group prepares to face the dragon for the last time, they look on in horror as a magical storm conjured by the mermaid council begins to destroy the dragon. While Zac and Mimmi face the dragon and attempt to free Nerissa with the bracelet, Weilan and Ondina race to the moon pool beg the council to stop what their doing and give Zac and Mimmi a chance to save their mother. Their pleas prove futile when Veridia informs them that the magic they unleashed is now beyond their control. When Mimmi and the dragon suddenly disappear, Weilan is horrified at the apparent loss of her friend but overjoyed when she and a newly freed Nerissa emerge from the water.
At Rita's grotto, Nerissa reveals that Aurora used a spell to turn her into the dragon and was sent to attack Weilan's pod on Aurora's orders. She also confirms that she had indeed followed Weilan to Mako in the hopes of seeing her children again. Weilan and Ondina then look on in joy at seeing their friends finally reunited with their long lost mother. Afterwards, Weilan sneaks into Uncle Shen's shop and fixes a piece of his merchandise he had been having trouble with to thank him for all the support he had given her.
It is then revealed that Veridia gave Weilan a moon ring to thank her for her help in protecting the pod. She then contemplates returning to Shanghai to get the Eastern pod started again and is surprised when Ondina offers to help her, showing just how strong their friendship had grown.
Sassy and smart, Weilan initially clashes with Ondina, who blames her for bringing the dragon to Mako. She has hidden depths of talent and knowledge of an Eastern mermaid. Although she can be headstrong like Ondina, Weilan is a friendly fun loving mermaid who gets along with others easily. She is patient with Ondina despite her initial hostile behavior towards her. She also is friendly with Zac despite the previous history of mermaids and mermen, even becoming close friends with the latter. Weilan also has a sensitive side shown from the hard times she suffered throughout her life. She is deeply hurt over the loss of her pod even shedding a tear about it and later shown to feel genuine guilt expressed through tears when she causes Evie to lose her tail.
While attending school on land, Weilan shows immense talent in her academics, earning herself straight A's.
Weilan possesses the ability to transform into a mermaid ten seconds after physical contact with water. Once her body is completely dry, she turns back into a human along with the outfit she was wearing before she transformed. As a mermaid, she has the ability to swim at super speed of 600km/h, hold her breath for more than fifteen minutes, and dive at a depth lower than any ordinary human being. She utilizes her magic with Chinese kung fu style and knows certain moves known only to Eastern mermaids, such as "turn the tide", a defensive move to deflect magic, a spell to transfer knowledge (though she lacks the experience), etc.
In "A Visit From the East," she uses telekinesis to make David go flying backwards and makes the crates go flying. In "Turning the Tide," she uses telekinesis on Zac to send him flying backwards during her training with Zac. In "Mopping Up," she uses Telekinesis to levitate the mop
- The name Wei means as a feminine name comes from 微 "small" or 薇 "rose." Lan is a Chinese name meaning orchid (蘭).
- Her name was misspelled as Wai Lan in one article.
- After the Water Dragon was dealt with, Weilan expressed an interest in going back to Shanghai and restarting the Eastern pod.
- She has her own apartment in Shanghai.
- Weilan did not have any hardships with Zac, unlike other mermaids when they first meet him before. This is possibly because she did not grow up in a pod, so she wasn't taught to fear mermen like other mermaids. She even expresses a strong interest in meeting him when Mimmi tells her about him, suggesting she knows how hard it is to find one nowadays.
- Although she's from China, Weilan speaks with an Australian accent.
- She is the only mermaid that is not a former enemy of Zac's.
- Main article: Weilan/Gallery