All forum games go here. This is not for discussion of video games or any other kinds of games, though, so please put any such posts in General Discussion.
Depending what you mean by help its either "The Trap" when she helped Ulrich with his broken arm, or Frontier when she helped Yumi get out of suspension with the principal and allowed her to get to the factory with Jeremie's laptop.
As for Lyoko is Cool's question, that would be Mr. Puck.
First episode where Christophe M'bala first had a (small) speaking role.
To answer my own question, it was Final Mix. He was the one who introduced Aelita as the dance's dj.
To answer Lyoko is Cool's, I would say it was actually Unchartered Territory. I would of said Frontier, Ghost Channel, or Code: Earth, but they all had a bright red tower in 'em.
To Rodri's question, does pajamas count? If so, I'd say A Great Day. If not, my next guess would be Tip-Top Shape, though that would be way to far out another underwear scene.
Heidi is the name of the girl that Odd asked out in "XANA's Kiss" and the girl who said "I like Odd" in "Routine". And I want to say the answer is "Log Book", where she was shown helping Ulrich pull Jim back into the bus after he broke the window.
First episode where Aelita killed a monster by herself.