What do you mean the area under the Simpsons ride?
I know that there is almost like a tent like area outside where you wait, if that is what you're talking about?
From my experience when you enter, you can either get into the express line, or the regular line (above the entrance is the Krusty the Clown head). While you wait outside you will eventually get to a certain part where you can go one way, or another when a employee directs you. One line will direct you directly to a line that will lead you into the building, while another line will direct you up a ramp, while you walk up the ramp and you wait up there, and eventually you will go into the building as well (but you'll be in an upper level).
There is a loading area there for the vehicle that takes guests to the lower lot, who are unable use the Starway escalator. A guest can get there by using the elevator located to the right of the top of the Starway.