Yes my poll sucks oh well.
It's an old episode, from the middle-ish of Season 1 but it needed a thread (as do three other episodes I plan on doing) so...here it is xD
Synopsis: It's been a year since the team met Aelita, and they decide to do something to commemorate the occasion. But XANA traps Odd and Jeremie in one area of the factory with equipment trying to tear them apart, and traps Yumi and Ulrich in the elevator-- with Sissi no less --leaving Aelita alone in Lyoko to fend for herself, complete with a Krab stalking her every movement. Not to mention that Ulrich's got a broken arm from a sudden drop the elevator took (Tower of Terror anyone) and, to complicate matters with Odd and Jeremie, they've gotta pass through the boiler room, with the boiler set to explode any time..
This has always been my top favorite episode and remained as such until I saw "The Key" much, much later, and even now is in the top five. There are a number of good moments in it.. Although I think the most "famous" might be what Aelita did to the poor Krab, dropping out the ground right from under it xD. Not to mention that there were more "Sissi showing her nice side" moments. Overall, a pretty good one ^^ At least...by my standards xD;