Guinea pigs

Guinea pigs are little animals that still exist in the 31st century. In the "Terror at 500 Feet" segment of Anthology of Interest I, Professor Farnsworth feeds a guinea pig to Zoidberg to make him bigger and defeat the 500 foot Bender. Bender owned one who died by the events of In-A-Gadda-Da-Leela. According the Countdown to Futurama, the future episode "Cold Warriors" will feature a guinea pig astronaut.