Principal Skinner takes Patty to what he claims is the premiere of one of the Space Mutants movies. Movie premieres are major, packed events, and certainly would be for a film in what is apparently a popular series in the Simpsons universe. This looks like a traditional weeknight showing with tons of empty seats in the theater, certainly not the crowd and fanfare one would expect from a premiere.
Hans Moleman's driver license clearly says his name is Ralph Melish. This may be intentional as Moleman is often confused.
At the revolving restaurant, Skinner berates the waiter as one of his former students "Class of 71", saying he's nearly 30. If he were class of 71, he would be nearly 40 at the time of this episode.
After Bart uses herbicide to write his name in the grass in 40-foot letters, Principal Skinner punishes him by making him re-seed the lawn by hand. This however wouldn't work, as the herbicide would kill the seeds; the topsoil would need to be replaced first.