When Bender is putting butter on his popcorn, a man in the background is missing his eyes. It's possible that he is some alien species that does not have eye on its face.
The color of the eyes and teeth of robot elder on the far left changes from red to yellow.
When Fry and Leela are asking the robot in the Tetris scene if they have seen Bender, there is a four purple cubes in the right top corner. However in the next scene it only shows three purple cubes in the right top corner.