When Bender wins the poker tournament with five kings, Leo Wong holds up five fingers (on one hand). But all the characters in Futurama only have four fingers on each hand. (Confirmed on DVD commentary).
When Zapp Brannigan tells Leela to surrender by waving her shirt in the air, there is a shot of Leela pulling her shirt off whilst the camera pans up and we see a shot of her breasts for a few frames. Confirmed on the Audio Commentary. However neither of her breasts have nipples; possibly as a result of her being a mutant.