In Futurama, the year 10,000 holds 5 Statues of Liberty from different species. Humans, Birds, Monkeys, Cows, and an Alien blob sort of thing.
What is that alien race? Was the alien race ever shown in another other episode?
If you listen to the dialogue, you'll hear Fry lamenting about how we've destroyed our own society. To make matters worse, so did the apes, birds, cows, and… "I don't know, is that a slug, maybe?" Those are the words Philip J. Fry uses when he sees their statue, but can't place what they are. I don't think the writers were actually trying to give a specific race, but rather thought that it would be funny to see Fry (and the audience) struggle in an attempt to identify the vague-looking statue of…something.