Pennington is a Bumpty found in Paper Mario: The Thousand-Year Door who lives in Poshley Sanctum located in Poshley Heights. Mario first meets Pennington on the Excess Express. He mistakenly calls Mario "Luigi". When Pennington says "Luigi", the text is in green.
When Mario first enters the Excess Express and meets Pennington, they were supposed to figure out the weird things happening on the train, but Mario was clever enough to figure out himself that Smorg was holding all the passengers hostage, except for Mario himself. Pennington thanks Mario after solving the mystery.
When Mario goes to the Poshley Sanctum in Poshley Heights after climbing off the Excess Express, he attempts to enter the palace, but the place, however, was locked. Pennington then comes along and unlocks the stadium, allowing Mario to enter. He the reveals that he is the manager of the stadium and that being a detective himself is one of his hobbies.
When Mario goes ahead and fights the Shadow Queen in the stadium, everyone cheers on for Mario Goldbob and his family, along with Toodles are seen cheering on for Mario, mistakenly calling him "Gonzales". Pennington then gets confused if Mario's real name is Mario or Gonzales. Even after Mario defeats the Shadow Queen, Pennington shortly reprises his habit of calling Mario "Luigi", but corrects himself afterwards.
- Francis in Super Paper Mario has a Pennington doll.
- Before Mario fights the Shadow Queen, he says "Go Luigi...err...Mario?", showing his confusion on Mario's name.