Squidward is not on the till when Plankton first finds himself in the Krusty Krab.
When Plankton says, "I hope you like gray", Squidward's eyelids are the same color as his skin.
When SpongeBob raises his arms after calling the beachgoers over for ice cream, if you look closely as he says he hands the ice cream out, he never lowers his arms.
When Larry rescues SpongeBob and Patrick, the water is ankle-deep, but earlier, Patrick is shown sinking multiple times and out far enough to not be ankle-deep.
During the montage where SpongeBob and Larry do fun lifeguard things, SpongeBob is shown lifting a barbell with two cups of soda and is clearly struggling with it. However, when he has to rescue Patrick from drowning later on, he borrows a boat from a couple and lifts it effortlessly.