I agree with Gorky in that I love the loser and pathetic Zoidberg, although I actually have always found it hilarious when he does stand up to the crew.
"Hey Zoidberg, get in here!"
I agree with Spacedal. I don't think that Zoidberg in SotC was really "out of character", per se, but just a part of Zoidberg we don't often see. We've seen with that quote and with Crustacean in Love that Zoidberg CAN be passionate and excitable, and can occasionally stand up for himself. It just doesn't happen often, and when it does, it's so unexpected that it's hilarious.
I agree. I mean we've seen Zoidberg going crazy in previous episodes where something he wants or he himself is threatened (screaming at Coilette to get the cake he wants, going beserk over anchovies, mating frenzy, getting upset when he is being ignored in the Parabox). Zoidberg is pathetic, but we have been shown that he has a boiling point many times in the past (pun not intended, hehe.) He gets lonely and depressed very easily, and once he reaches a certain point, he will vicious defend what he wants, whether its the last can of anchovies, the girl he loves, or anyone pushing him down in the pecking order. He's very much a Beware the Nice Ones type. So for the most part he will put up with all sorts of physical and verbal abuse, but if it gets overdone, then we see another side of him. Its just done rarely enough so it becomes surprising when it happens, but not so rare that it should feel out of character.
All of the mild mannered/rational characters have id moments (Leela has slowly become more violent and aggressive, Amy barely restrains the desire to eat herself into obesity) and Zoidy is no exception.