>>110613
Alright, this is one of the ideas I have, I was thinking about the one episode where everyone ate chili that had Chemical X in it and it resulted in the city getting attacked by a giant gas monster, so maybe Buttercup found the chili so delicious that she ate around 10 bowls worth of leftovers when she got home. (Assuming that there was any leftovers of the chili back at her home.)
And later that night, Buttercup began severely bloating as the gas in her body rapidly expanded, making her look like a giant fat balloon.
So, wanting to avoid any embarrassment, Buttercup decided to leave through the window in her room.
(And getting stuck in the process because her body was already ballooning fast, but she managed to free herself in time before it was too late)
Eventually, Buttercup made it outside of the city, but by that point she was a giant fat blimp that was ready to burst.
And after what felt like ages, Buttercup finally lets loose a massively long and loud fart and returns to normal, then she goes back home and heads back to bed like nothing ever happened.
(Although, Buttercup is still relatively fat and obese even after her massive fart, she probably still has more gas in her)