So back in the day there was a show called Mystery Science Theater 300. I loved that show (though i was born after it was cancelled) so anyway My older brother and I wanted to do a series on youtube like it. Like in the show a movie would be shown as if it were being shown in a movie theater and the silhouettes of the audience (my brother and I and maybe a friend) would be seen at the bottom of the screen.
(like the picture above) Could i be able to do this in After Effects?
Sure! The question is how you would create the foreground (people in the audience). If you film yourselves on a green screen of sorts, you might not even need After Effects (Premiere should do the job).
The most basic thing you need here is two layer: the foreground and the background (the actual video).
I'd make all those theater seats with either a shape layer or masking a solid. The subjects sit on stools or something. In front of a chroma key background. Then position & scale as desired.