Julien sees the Lemur School reunion as a way to relive his glory days, but his old flame Karen and his foe Karl have a dangerously different agenda.
In the plane, Julien is excited he can fit into his old tuxedo. A few minutes later, Clover walks in and asks why Julien is in formal wear. King Julien and Maurice say they are just getting ready for their lemur school prom reunion. Julien, Mort, and Clover all reminisce about their different prom experience. Julien gloats about being the best of his class in Lemur school, and how he is sure to win the title of prom king again. Julien then brings up his ex-girlfriend, Karen, who sadly got eaten and killed by a foosa. Julien says that she may rest in peace.
At the reunion, Ted is giving out name tags for everyone, but then stops to welcome Julien to the reunion. Every lemur cheers for Julien. Julien, enjoying the attention, walks to get his name tag but runs into Karl. Karl's reason for being here is because he was in the same classes as Julien, but Julien ignored him. Julien tells Maurice that Karl is acting suspicious, which Maurice agrees with and says this reunion was a bad idea. Clover, there for security reasons, promises Julien that she'll keep track of Karl.
During the prom, Julien is having a blast dancing, while Clover is watching Karl drinking some punch. Julien stops dancing as he sees his old flame Karen appear in front of him. Julien, shocked but glad Karen is back, apologizes to her about her believing she was eaten. Karen replies "after you stood me up". Julien is confused, but then remembers. Karen says it's fine and she's sure Julien had a good reason for standing her up. Julien remembers Ted trying to get Julien's tie just right, but it never met his satisfaction.
Julien says to Karen that after all the time he has known her, he never got to see under her glove. Karen is going to show her hand under her glove, but gets interrupted by their favorite song. Karen asks if Julien remembers the dance routine they created, to which Julien replies he practically invented it and the two start dancing.
Back with Clover, she watches Karl go into the bathroom, wondering what he's up too. She hears the noise of a horse race announcer from the toilet. She opens the door to find only a recording.
Back at the dance, Julien and Karen are finishing their dance routine with cannons firing. At the end of dance, Julien asks if she really meant it when she told him he could see under her glove. Karen says yes and takes off her glove, revealing a monkey's paw. Karen says she likes to put hair on it to feel more normal. Julien, grossed out by her hand, tells Karen that she is normal.
Suddenly, video starts to play. Julien thinks it is a tribute video to him. The video actually shows that the lemurs were actually friends with Julien in lemur school only because he was the prince, they laughed at his jokes, and let him win everything. When Julien took the title of prom king, Ted was actually voted prom king but was forced to give it up to Julien. Julien laughs, thinking this is a joke from Karl, but when Julien sees the projector, Karl isn't there. Clover appears, apologizes to Julien for losing Karl. The video then talks about Maurice, who was paid in mangoes by Uncle King Julien to be Julien's friend. Not wanting this to be involved in Julien, Maurice frantically rushes and hides the picture and tells Clover to turn it off and Clover breaks the projector. Heartbroken, Julien asks Maurice if this is true, and Maurice says it started as a job, but grew into actual friendship. Julien doesn't believe Maurice, runs into the jungle, and tells no one to follow him. Filled with fury and sadness by these lies after all these years, Julien runs off, crying. Clover says to Maurice that she'll talk to him, and lets Ted comfort Maurice, when he starts to cry, beleiving that he'll never going to be his best friend ever again after he lied to him.
Clover looks through the jungle to find Julien, but gets knocked out by a club.
Julien starts sulking even more after realising that no one followed him, and believes that no one really loves him, much to his disappointment. Karl then appears calling for Chauncey and yelling to him that they're going to celebrate, until, to his surprise, he notices Julien sitting on the log. Julien blames Karl for making the video and humiliating him, but Karl says it wasn't him, because videos are too simple for his tastes. Karl then thanks Julien because if it wasn't for him ignoring him in lemur school, Karl would have never met Chauncey. Karl then leaves Julien by a spring trap.
Julien is now mad that even Karl has Chauncey while he has no one. Karen then shows up, saying she thought Julien could use a friend. Julien initially refuses Karen, assuming she was also paid, but Karen says she thought Julien was the coolest, sweetest, and most handsome lemur in the school and she still does. Karen then brings out a boom box and starts playing their song. They both start to dance.
Julien and Karen show up at a waterfall and Karen says that it is the place they were supposed to meet on prom night. Julien then falls into a rope trap. Julien realizes that Karen was the one that made the video and becomes furious. Karen planned the whole reunion to humiliate him like he humiliated her. Julien asks what of the feelings she had for him, and she says it was a lie, that she was only using him so she could become prom queen and possibly queen. Karen then pulls out a whistle and blows it, calling the foosa to eat Julien.
Back at the prom reunion, Ted is still hugging Maurice but Maurice says he has had enough. Maurice is worried that Clover and Julien haven't come back yet. Clover suddenly appears tied up with a gag in her mouth. Maurice removes the gag and asks what happened, and Clover replies that the whole thing was set up by Karen.
While waiting for the foosa, Karen is tormenting Julien with her hand. Once the foosa show up and Julien is about to be eaten, Clover and all the lemurs from prom show up to help. They say they are sorry to King Julien and that they care about him, except Hector (obviously). The lemurs charge at the foosa, but run screaming, afraid of the foosa, leaving Clover to fight alone. While Karen is laughing, Clover attacks her. Karen asks her why they girls don't stick together. Clover admits what Julien did was wrong but it's no reason to kill him. Clover cuts the rope leaving Julien to fall, but Maurice catches him. With everyone about to be eaten by the foosa, Karl arrives, saving them, claiming he and Julien are enemies and only he is allowed to kill him, not Karen. Karl fires another laser, making the foosa run away. Karen yells at the foosa to eat King Julien, not run away, but a foosa from behind her eats her (this time), leaving only her glove. Julien picks up the glove and wishes Karen may rest in peace. He thanks everyone for coming to rescue him and comes to realize they do love him. Julien then thanks Karl and asks if they are friends now, but Karl insists they are eternal enemies and he will destroy him when he least expects it, and laughs as he leaves by spring trap. Julien's spirit is finally healed after learning that they really love him, until Mort appears behind his legs and tells him that he loves him the most. A disgusted Julien jumps away from Mort and tells him that if he would have loved him then he wouldn't be obsessed with his feet, with spring trap sends Mort away, with Mort yelling:"You're my everything!"
After Karen's death, the lemurs are back at the prom dance. In there, Maurice apologizes about him being hired to be Julien's friend, but Julien is fine with it because he is his best friend. Maurice says everything turned out okay in the end, but Julien says there is one more thing to be done. Julien makes an announcement and proclaims Ted prom king, and he says it should have been like this all those years ago. Ted is going to say his thank you, but Julien kicks him to the crowd and says "less talking more dancing, Ted", as they start to dance, ending the episode.
- Karen (first appearance; death)