On one of the walls of Coolsville there is a t-shirt that reads "I Didn't Do It", a phrase Bart made popular in the episode "Bart Gets Famous."
"Shapes" is a spoof of "Curves", the health and fitness club for women.
The scene showing people in the gym dancing on treadmills is a spoof of the music video for the song "Here It Goes Again" by OK Go. (The song also plays during the scene.)
One of the guest artists asks if Lisa knows anyone at Batman, because he really wants to draw Batman. Alan Moore, one of the other guest stars, has worked off and on in Batman projects. Elements of his work have appeared in Batman: The Animated Series (1992) and the direct to video movie Batman: The Killing Joke (2016) was largely based off Moore's Batman story of the same name.
Bart asks the new comic book guy who is stronger; The Thung or the Incredible Mulk. Both of these characters are parodies of The Thing and The Incredible Hulk from Marvel comics.