Candace (groans): This must be what it feels like to be pregnant.
Candace's medieval counterpart, Candavere, along with her friends Stacehilda and Jenavene, gain some nice bulges after a large banquet at the end of Excaliferb: A Further Adventure. In fact, there are two drawings depicting these here and here.
Finally, in Two Lads in Dangrabah, Candace swallows a submarine sandwich whole, which causes her stomach to bulge out significantly. Because in this story, she is a genie, she uses magic to shift the fat in her gut into other places, but since she doesn't do this immediately, it appears that she doesn't seem to mind being bigger.
Funny, all three stories happen to be written by the same fanfic duo.
Sonic the Hedgehog's Rouge the Bat unknowingly fattens herself up in Rouge's Weighty Frustrations. She doesn't even notice her larger belly for quite some time, until she decides to go on a heist, where her new bulge gets her stuck in a small space... twice.
This happens to Dawn in the second chapter of the Total Drama fanfiction, Total Drama Prison. She drinks four whole bottles of aged soda as part of a challenge. Not only does her stomach bloat up and start aching, which lasts for the rest of the chapter, but she also gets the hiccups from drinking too much.
Scooby-Doo's Daphne Blake purposefully gains weight in Outfitting A Wide Wraith, in order to participate in a Big Beautiful Woman competition. Obviously, many jokes are made at her expense, but Daphne seems to be proud of her new figure.
Daphne: I don't know how you and Scooby ride in the back all the time, Shaggy. All that shaking made me feel like jello…
Another example of a story revolving around this trope is A Pokémon Gaining Adventure. There are quite a few people who gain weight, but the story mostly revolves around Misty.
A Naruto fanfiction called "Sakura, Hinata and the Buffet" has Sakura fatten up Hinata after both characters end up in a lesbian relationship.
Global Inflation has this happen to pretty much all the leads of Axis Powers Hetalia, as a result of massive inflation in all of their economies.
In a Sailor Moon fic, Cosmic Warriors, Naru and Usagi notice several customers have this when they arrive at a pancake shop.
Plasma's Folly contains a non-comedic example: assuming his Zekrom form, a famished Ben swiftly devours a platter of food, swallowing whatever he can fit down his throat whole. This is good and fine, until he reverts to his human shape while retaining the contents of his stomach. Nearly leads to Death by Gluttony.
