Yumi suggesting the caricative party to help victims in Japan to Mr. Delmas:
Yumi: I thought it was a good idea... Mr. Delmas: That is not a good idea, Ms. Ishiyama. Yumi: But... Mr. Delmas: That is a great idea!
Ulrich actually gets sick of Yumi, argues with her again and leaves her dealing with preparing her party alone, refusing to help. Who gets him to come back? William, of all people, by saying she needs him and admitting he was such a jerk lastly because he was sick of being seen as the bad guy. Then both of them come back and help Yumi.
The team calls off their attempt to kill XANA when Aelita's mother is revealed to be alive and in Tyron's employ, even when Aelita herself wants to continue, because they know how much she wants to see her and know that destroying XANA would end any chance of that. Also, Aelita tell that she loves Jérémie no matter what, while he, Laura, and William are overhearing.
Aelita and Yumi hanging out with Sissi in "False Pretenses", especially the ending. It definitely shows that they weren't kidding around when they said Sissi is their friend now at the end of the previous series.