The whole time Nicky and Alex are playing with the Elvis puzzle, none of the pieces are in place, they're just scrambled. Suddenly, in less than five seconds, they are one piece away from being finished.
The exterior shots of the Subway are New York trains, not San Francisco's BART or MUNI system.
Jesse says that one of the main reasons he is valedictorian is because he dropped out of high school then dropped back in, so he would be a good example. But Jesse is in the adult continuing high school where everybody else would also have been dropouts that dropped back in.
When they're stuck in the subway and Jesse tells the other school dropout about Nicky and Alex struggling with an Elvis puzzle, he mentions that Elvis' left sideburn was the last piece. But when the puzzle is shown, it is Elvis' right sideburn that is being shown.