Drawn by Zombineko over on Furaffinity! Thanks very much!
For those confused about the comic, Swift Brush is a colt who is incontinent from birth, so he constantly has to wear diapers. He has a very big crush on Sweetie Belle, who accepts him, as in my world of OCs, she's a constant bedwetter, so she has to wear diapers every once in a while. So, that's why she's so easily able to use diapers around him, and that's why they're fine with changing each others diapers.
For those who can't read the text:
Panel 2: Swift Brush: "sigh What's taking him so long to get that spare wheel? We've been sitting here for fifteen minutes…" Sweetie Belle: "stomach rumbles"
Panel 3: Swift Brush: "You OK, Sweetie Belle?" Sweetie Belle: "Y-yeah. I just hope he gets back soon. Those double hayburgers and milkshakes I had aren't sitting well with me, and… I really gotta go to the little filly's room…"
Panel 4: Swift Brush: "You gotta go pee?" Sweetie Belle: "Y-yes! And poop! Bad!"