I don't know whether this has already been discussed, but I searched on Deja and didn't find anything about it. Sorry if I repeat something that has already been mentioned.
In the very first ep, when Fry and the chair fall down (in the Cryogenics lab) and there is a close shot of the fallen chair, you clearly can see Nibbler's shadow on the left (in 1999/2000!!!). What do you think does that mean? Will they actually travel back to 1999/2000 in one episode?