After seeing the buck swaps here and this episode, I actually think of teenager Mac as a little (and why not, handsome) videogame and science-fiction lover FREAK. His shelfs full with figures, merchandising, books...
Mac: I'm not a freak!
Me: Don't worry, everyone has a little freak inside.
Mac:Noooooo---!!
I think this is one of that episodes that wouldn't have a clear message if many characters appeared. As Bloo and Mac are the main characters it's obvious that this episode was intended to make their friendship deeper and more credible.
I like it when Mac says: That's weird. Only sugar makes me...and then he goes
