Truth Or Cosmoquences is the twenty-third episode of Season 4.
Timmy is enjoying lemonade, when an owl brings an invitation for the Fairy High School reunion. Cosmo does not want to go because he is scared to face people when he is not "rich and successful". So Timmy and Wanda agree to help Cosmo impress people at the reunion. Cosmo will pretend he is rich and married to a rich Celebrity. He is so rich that he has a secretary named Wanda and even a butler named Timmy. The problem starts when Juandissimo wants to flirt and dance with Wanda... and Cosmo blurts out the truth. How will everyone react when they hear Cosmo tricked them?
The episode starts with Cosmo, Wanda, and Timmy playing outside. Timmy declares that playing ball with himself is thirsty work, so Wanda poofs him a giant pitcher of lemonade. When Wanda comments on how much he is drinking, Timmy responds that Turners have bladders of steel. That's when an owl shows up with a telegram for Cosmo and Wanda, and before opening it, Wanda pulls out a tiny mouse from Cosmo's green hair and gives it to the owl as a tip for his services. When he flies away, Timmy decides to chug down even more lemonade and Wanda reveals that the letter is an invitation to hers and Cosmo's high school reunion. Nervous at this, Cosmo grabs the letter, stuffs it into his mouth and asks "What invitation?" Wanda pokes his stomach with her wand, causing him to spit the invitation back out. Wanda mentions that high school was the best four years of her life while Cosmo proclaims it was the worst ten years of his. He then proceeded to poof in an old yearbook where he shows pictures of Luther (who was captain of the football team as well as the main bully for Cosmo during his time at high school) and everyone else picking on him in school. Wanda asks him what he has to worry about, saying that a reunion means seeing all the people they used to hang out with. Timmy smiles saying that no one expected him to be a billionaire mogul with a beautiful trophy wife. Cosmo chuckles nervously at this prompting Wanda to ask him what he told their old classmates.
When they arrive at the reunion to sign in, Cosmo is dressed in a fancy tuxedo, complete with a top hat and monocle. He then explained how he was the very rich Cosmo, the inventor of Wandos 2.0, which was the operating system of everything magical in Fairy World. He introduced Wanda as his dowdy, unmarried, personal secretary; he introduced Timmy as his butler with a cast iron bladder; and he even brought pop-diva Britney Britney who was "clearly not hypnotized" to pose as his beautiful trophy wife. After drinking the rest of his pitcher of lemonade, Timmy turned to Wanda to ask where the bathroom was. Wanda said that she told him to go before they left, and Timmy said, "No. What you said was, 'We are not posing as a butler and a secretary just to pose for the lies Cosmo told people.' Then Cosmo started to cry, and you said, 'Oh. Okay.' And now we're here." Cosmo rushed over with two nametags, proclaiming "Butler" and "Dowdy", explaining how they would just be in there to impress a few people with his false life and be out in no time. Wanda and Timmy each ripped their nametags off in annoyance, walking toward the gymnasium door; however, when Timmy tried to open the swinging door, he merely just ran into the wall. Wanda explained how the doors were just painted on because you didn't need doors in a fairy high school because you just poof from room to room, and that doors were for chumps. Cosmo and Wanda then poofed them all inside the gymnasium where Timmy mentioned that he really had to go to the bathroom, but as long as he didn't think about it, he would be fine. That's when he saw that the theme of the reunion was "An Ode to Running Water" complete with fountains.
Cosmo starts schmoozing with his former classmates when he suddenly hears the voice of his ex-tormentor, Luther, in the crowd. When Luther says "I think you know why I'm here..." while reaching into his jacket, Cosmo cries "Don't kill me! I'm rich!" However, Luther was reaching into his jacket for a resume, wanting to be Cosmo's bodyguard. This excites Cosmo, knowing that people really do think he's super rich and powerful. Wanda realizes what he's thinking and is about to lecture him; however, before she can even start, Cosmo hires Luther and orders him to get rid of his secretary. Meanwhile, Timmy is still attempting to go to the restroom. He found a door for the boys bathroom, running into, remembering that doors are just painted on the wall, and he hopes they don't stay long. Two hours later, they're still at the reunion and Timmy is very uncomfortable due to his full bladder. He finds Cosmo with a group of fairies where he is mesmerizing them with more of his lies, and he attempts to wish himself into the bathroom; however, Cosmo cuts him off nervously, asking him to go get him and his friends more punch. He and Wanda are the ones to get the punch, where he has a conversation with Wanda about how they should leave, but Wanda rebuffs him saying "What else could possibly go wrong?"
That's when Juandissimo shows up at the reunion, causing Cosmo to sweat nervously as Juandissimo is the only one there who knows that Cosmo is lying through his teeth. Cosmo asks what he's doing there, and Juandissimo reminds him of the one year he was an exchange student from another school. Then Juandissimo goes on to speak of how coming to Carl Poofy Pants Fairy High School was the first time he met, saw, and heard Wanda, and that now he wished to dance with her. Cosmo hops in between them, yelling at him to stay away from his wife. The crowd gasps, and Juandissimo tells him that that he would never come between Cosmo and his wife—the fantastic pop-diva Britney Britney. Cosmo chuckles nervously while Juandissimo knocks Cosmo out of the way, grabbing Wanda by the hand, insisting that Cosmo wouldn't mind if he danced with his dowdy, unmarried, personal secretary. Wanda watches as Cosmo lands in Britney Britney's lap, and angrily proclaims, "No. He can't." It is then that Juandissimo starts dancing with her, and Cosmo rushes off to speak with Timmy about the situation.
Timmy suggests they go somewhere quiet to think, such as the boys bathroom; however, Cosmo rejects the idea, instead claiming that all he needed was a refreshing glass of lemonade. Timmy, still about to burst, watches in agony as Cosmo guzzles down the drink. After he's done, Cosmo then decides to take a quick trip to the boys bathroom. When he poofs away, Timmy falls to his own knees, screaming for him to take him too. When Cosmo comes back, he proclaims that going to the bathroom was thirsty work and gets another drink. This angers Timmy, who grabs his godfather and asks him what's more important: telling lies to impress his fair-weather friends, or his love for Wanda who had always been there for him. He then takes another sip of water, causing Timmy to pass out. Cosmo then takes out his yearbook, looking through all the signatures pages to see they were all empty except for a single signature which read: "Cosmo, I will love you forever. Wanda." Cosmo closes the book, hugging it to himself and happily and realizes that Wanda is the one person in his life who always loved his true self. However he was still unsure of what to do. He looked back and forth between the people he was impressing, and Juandissimo dancing with Wanda. Finally when he saw Juandissimo stop dancing and begin kissing Wanda's hand, he knew what he had to do, until the hypnotized pop diva waltzed in front of him and said "hot tub" to which his decision slightly faltered again. However, when Juandissimo asked Wanda if she wanted to see his Diploma of Love and poofed in a piece of paper, Cosmo finally snapped not being able to take it anymore, poofing in a dragon which burned both Juandissimo and his phony diploma to a crisp.
Timmy then jumps in with Wanda, wanting to wish to go to the bathroom; however, he is interrupted by Cosmo wanting to make an announcement. It's then that Cosmo comes clean. He tells everyone that he isn't really rich or the inventor of Wandos. Timmy is actually his godkid, Britney Britney is just hypnotized to pose as his trophy bride, and Wanda is his real wife. Wanda proudly grabs Cosmo and the two embrace. Timmy, not able to take anymore, runs off to find somewhere to relieve himself. Cosmo and Wanda share a kiss, and Cosmo is surprised to see that no one is angry at him as he has done something none of the other students have ever done before apparently. In fact, Luther reveals to his fellow students that he's no longer captain of the football team (he no longer plays football anymore for some reason), but instead has taken up ballet (dubbing himself as lord of the dance). Another fairy reveals that she was wearing a wig to disguise her goofy rainbow colored hair, and one fairy revealed that he was actually a leprechaun. It was also revealed that the messenger owl from earlier doesn't eat mice, but that he actually ate leprechauns. He then goes after the leprechaun with the leprechaun trying to outrun him.
Cosmo and Wanda are hugging once more, with Wanda speaking proudly about how Cosmo didn't need to lie to impress anyone. Cosmo then strips down to just his underwear, proclaiming that he doesn't have to lie anymore, and that it's a relief. That's when Cosmo and Wanda poof in to glasses of punch and start drinking them. Timmy then walks by happily saying: "Speaking of relief, whatever you do, don't drink the punch!" Which causes Cosmo and Wanda to stop drinking and open their eyes in horror, realizing that they're drinking Timmy's urine, then the episode cuts to a The End title card.