Goompa is Goombario and Goombaria's grandfather. He is an elder Goomba and has extensive knowledge of the world, which comes from his adventures as a youth. In his prime, he used to travel the globe with his friends Koopa Koot and Bootler. Now an elderly grandfather with back aches, Goompa has taught his grandson everything he knows.
Goompa lives in Goomba Village with the rest of his family. In the beginning of Paper Mario, Goompa is fixing the veranda of their home with a Hammer. When Mario attempts to leave the village, Kammy Koopa appears and, using her magic, creates a yellow block that prevents Mario from leaving. Mario decides to ask Goompa for his Hammer and walks to the veranda. Unfortunately, the veranda has fallen apart, causing Goompa and Mario to plummet to the ground below. In order to get back to the village, Goompa temporarily joins Mario, and in lieu of fighting, he teaches Mario how to use the game's battle system and gives Mario his Hammer after it is found. Goompa also gives Mario the Power Jump badge after getting back to his house, and goes on to tell Mario how to equip and use badges.
One of the favors that Koopa Koot asks of Mario is that he retrieve a Tape that had been lent to Goompa a long time ago. When Mario retrieves the tape, he is curious of its contents, but Goompa refuses to tell him what is on the tape, commenting only that he enjoyed listening to it. During the party's quest to save Peach, Goompa writes a letter to Goombario, which the player can read at the Post Office in Toad Town. Mario can also find a letter for Goompa by hitting the tree at Kolorado's camp in Dry Dry Desert after Chapter 4 has been completed. Should Parakarry deliver it to him, he rewards Mario with a Star Piece.
- He's my grandpa, Goompa. He knows oodles of stuff. Ever since I was a kid, he's been telling me fantastic stories of his youth.
- According to Russ T. after chapter 7, Goompa used to be a famous fighter and sparred with The Master when they were young.
- Goompa has a C-Down command like all partners. In the beginning of the game when Goompa acts as Mario's partner, pressing C-Down will make Goompa move behind Mario if he isn't already.
- His name appears in the coding of the game in Mario's list of partners along with Goombaria and Twink, suggesting he was originally going to assist Mario on his quest. He, like all of the removed partners, has an identical icon to Kooper's.
- In the Crystal Palace, a Duplighost attempts to disguise himself as Kooper, but somehow ends up impersonating Goompa instead, down to his mannerisms.
- It is never revealed which, if either, of the Goomba family's parents, Goomama and Goompapa, are Goompa's children or children in law.