When Mario arrives at Rogueport at the beginning of the game, he sees a Goomba girl being attacked by Lord Crump. Mario helps her and defeats Lord Crump. Goombella thanks Mario and joins his party. She possesses very similar abilities to Goombario from the original Paper Mario, as they have almost identical moves in battle and on the field.
Her Tattle ability gives the player mostly helpful information on places, people, enemies, etc. Like Goombario's summaries, Goombella inserts her own little opinions in her descriptions, some of which are humorous. For example, she shows signs of resentment upon reading the "underlings of underlings" comment her book says regarding Goombas, comments about being jealous of a Paragoomba's wings, and points out that it's nice to have access to a bathroom now and then (that's a field-only one, stated in the Glitz Pit's major league locker room, where the bathroom is always occupied).
Goombella also has a tendency to break the fourth wall. For example, in Glitzville she mentions how far Cheep-Cheeps have come since Super Mario Bros., and in Twilight Town, she says that if there weren't people like the gatekeeper in every town, games would be beaten too easily. Both times she stops abruptly after she says the comment, seeming to point out that game characters know about the fourth wall but aren't supposed to talk about it.
At the end of the game, Goombella begins to tell Mario that she is in love with him, but then changes her mind and keeps her secret. She becomes Professor Frankly's research assistant at the very end of the adventure.
- Her name is probably a portmanteau between "Goomba" and the female name "Isabella".
- Goombella makes a cameo in the Nintendo Monopoly board game.
- Goombella may be a Headbonk Goomba due to the fact her skin is pink and and attacks by using "Headbonk", just like a Headbonk Goomba.
- Goombella breaks through the fourth wall twice when tattling, and twice otherwise.