Goombario is the first of Mario's many party members in Paper Mario.
He is very much like his other Goomba bretheren, the only difference being that he wears a blue baseball cap and appears to have slightly stumpier teeth than other Goombas.
When Mario has been knocked unconscious by falling from a great height and having just battled Bowser, Goombario's family takes the unconscious plumber to Goomba Village, a tiny village where peaceful Goombas live. Goombario, being a young boy, is naturally very energetic and easily excited, but he's also very smart. He is a big fan of Mario, as he says when he meets him. When Mario is about to embark on a journey, Goombario's father tells Mario to take Goombario with him, to which Goombario happily agrees. Throughout the journey, he remains very excited and wise, but sometimes also sneaks in some sarcastic commentaries on the enemies he and Mario face.
Goombario can use a special technique Goombas can only use in Paper Mario: Headbonk. Much like Mario, he lands on an enemy twice, but with his head rather than his feet. Despite living in the tiny Goomba Village and, at least very likely, having never fought before, he can tell Mario anything about any enemy with his Tattle ability. He can even use it to give Mario small hints on how to solve puzzles. With his Charge ability, Goombario can increase the amount of damage his next attack will do, and with Multibonk, he's able to endlessly Headbonk an enemy until the player misses the Action Command. He can hit enemies in the air as well as on the ground, but is helpless against enemies with spikes, fire or the ability to cling on to the ceiling.
Unlike other Goombas excluding Goombella. Goombario isn't hostile toward Mario.