While the 3 are trapped on top of the water fall, there's one scene where the rock that's keeping them from going over the edge isn't shown.
Bender sees the house of his old fraternity, Epsilon Rho Rho, which has a sign reading "ERR". However, the Greek letter Rho looks like the Latin letter P (as does its Cyrillic descendant), so the sign should look like "EPP".
Leela says of Mars University: "They planted traditional college foliage: ivy, trees, hemp..." but when she says "hemp," her lips appear to be saying, "marijuana."