Yumi!Odd: And if you hadn't noticed, I have a dynamite body! Better than yours. There... for example... (scratches his/her back) something's itching me in my back. It's a... I think it's the strap to your... hmm? Odd!Yumi: DON'T YOU DARE TAKE IT OFF, YOU HEAR!?
Same episode, Odd messing around with Yumi's body, flirting with Ulrich just to mess with Sissi (leading to a hilarious misunderstanding when Sissi leaves Yumi in Odd's body with a message about it for Ulrich), coming at school disguised as a Neko-girl and leading to a photo of Yumi and Ulrich together in the newspapers. Cut to Yumi's reaction at the end of the episode:
In one episode, Sissi, after being scared by one of XANA's specters, is sent by Ulrich to hide in his and Odd's room. Cue Odd partially awaking and noticing Sissi:
Odd: Uh? What's that? A dream? Sissi: Oh, Odd, I'm so scared! May I sit next to you? Odd: Oh, it's just a nightmare and soon I'll wake up!
Odd ending up cloned in three, and the numerous resulting gags.
All of XANA's xanatified victims in "Bad Connection". They're just so hilariously DUMB.
In episode 49, the gang finds themselves without weapons in Sector 5. So how does Odd take out a Creeper? Improvised boxing match, complete with sound effects!
Practically everything William clone says. The line he delivers in front of William's parents take the cake:
"To be specific, I'm a digitally-generated random polymorphic energy field controlled by a basic non-evolving behavioral program."
In the episode Contact, Milly asks Sissi to sum up the plot of the movie for the Kadic News:
Sissi: Uhm...well, that is...uh...its a love story, and at the same time it's a thriller with suspense! And of course, it's got a good dose of psychology, andandand...and it's very funny! A real comedy, and quite satirical.
In a fourth-season episode, Ulrich is in the doghouse for forgetting Yumi's birthday, so Odd gives him a hand by buying a present for him to give to Yumi. Later that night, it turns out that Odd bought a gift for Kiwi, too, but Ulrich thinks a necklace is a little classy for the dog. Back at Yumi's place, she opens Ulrich's gift and discovers... a squeaky-toy dog bone.
Aelita: You've already finished all you have to do?
Jérémie Clone: Piece of cake sweetie pie huh? What you think? Sure am done you're lookin at the man! (To Yumi) How's it going kid, you must of got all dolled up for me today? You won't believe the vibes I'm feeling right now.
Yumi: Hey, go back being Jérémie will you?
Jérémie Clone: Hm? It's just that, whenever I see you, I don't feel like I'm myself.
During the episode Final Mix, Jim is collecting everybody's tests, then stops and sees that Odd made his into an origami swan.
"...Well done, Odd, that's one of your best yet."
Two words: Odd's jokes.
Funny Background Event: Odd gets one in one episode. On Lyoko, his tail got shot at and caught on fire. He spent about two minutes flying around in the background trying to put it out. After the two minutes he FINALLY decides to blow it out when the camera focuses on him.
When the William Clone starts to try "personal initiatives, like trying to imitate Odd's stupid stunts" like launching stuff across the cafeteria with a fork (Odd was using food, William was using a glass cup).