Futurama is a great show. I'm not sure if it's surpassed good Simpson's for me but it's yet to get unfunny, so I would much rather watch a Futurama episode any day of the week. More importantly though it has a great supply of aliens to draw.
Nibbler is Leela's pet alien. She herself is not an alien though but a mutant. He likes to eat stuff and poop out dark matter.