Belly Bag is a major character in the series Uncle Grandpa. He is a magical fanny pack which has infinite space and contains all of Uncle Grandpa's supplies. He is also Uncle Grandpa's best friend. He has appeared in every episode, since Uncle Grandpa takes Belly bag with him pretty much everywhere he goes. He is voiced by Eric Bauza.
Belly Bag is a red fanny pack with buttons as his eyes and zipper as his mouth. He has two straps on his sides that serve as his arms and/or legs and he has two silver buckles on the ends of his straps.
Belly Bag's personality is a complex mixture of willingness to help and support his friends, a voice of reason, sarcasm, and jokes. As seen throughout episodes, he is always there to help Uncle Grandpa out with his endeavors. However, Belly Bag sometimes realizes that Uncle Grandpa doesn't always do the right thing, so he tries his best to steer him in the right direction even if it doesn't always work. Belly Bag is also EXTREMELY sarcastic. His sarcasm is especially shown in Funny Face (toward Mr. Gus about why he wasn't invited to the Funny Face party), Uncle Grandpa Ate My Homework (toward Dennis in response to Dennis's sarcasm toward Uncle Grandpa), Shorts (toward Uncle Grandpa in regards to him destroying an orphanage), Leg Wrestler (making a sarcastic joke about Uncle Grandpa and Mr. Gus being all tied up in the match), and Board Game Night (in response to his lousy dice roll). Despite his constant sarcasm, he's also constantly explaining himself (shown in Uncle Grandpa Ate My Homework and Board Game Night) and constantly backing down if ignored or told to be quiet (shown in Nickname, Driver's Test, and Shorts). He also seems to flirt quite a bit, though his flirting is a bit awkward and sometimes creepy (good example of this would be in Tiger Trails where he asks "What's stoppin' ya?" in a flirtatious manner in response to when Uncle Grandpa says "I could just kiss you!". Another good example is in Jorts when he oggles Mr. Gus's jorts with Giant Realistic Flying Tiger).
- Uncle Grandpa - Belly Bag and Uncle Grandpa are best friends and the two of them have never been seen without each other. Uncle Grandpa is the one who is seen interacting the most with Belly Bag and spending the most time with him. Whenever Uncle Grandpa needs something, he just reaches into Belly Bag and gets it out of him.
- Mr. Gus - Mr. Gus and Belly Bag don't interact with each other much in the show, but in the episode "Uncle Grandpa Sitter", Belly Bag was seen leaving Uncle Grandpa to go have ice cream with him, implying that they are good friends.
- Pizza Steve - Pizza Steve and Belly Bag are friends. They do not interact with each other that much, but they were making funny faces in the episode "Funny Face" and they were having ice cream together in the episode "Uncle Grandpa Sitter" without Uncle Grandpa. Belly Bag, however, has a tendency to spit sarcasm out at him (as seen in the Board Game Night short when he said "Sorry Buddy" when Pizza Steve got hit with 3 kids, a wife, and a mortgage).
- Giant Realistic Flying Tiger - Giant Realistic Flying Tiger and Belly Bag are friends but they don't do much together. However, Belly Bag was seen having ice cream with Giant Realistic Flying Tiger in the episode "Uncle Grandpa Sitter" and they were seen making funny faces together in the episode "Funny Face".
- He doesn't talk in the pilot.
- He is refered to as Fanny Pack and voiced by Paul Rugg in Secret Mountain Uncle Grandpa.
- A belly bag is actually a urinary storage article of clothing, thus making Belly Bag's name a possible inside joke.
- In "Treasure Map", it is revealed he likes fog machines.
- Additionally, he seems impervious to tear gas.
- As seen in "Uncle Grandpa Sitter", he enjoys eating sprinkles.
- It is suggested in "Charlie Burgers" that he may have the ability to see into different portals into different dimensions without having to go through them himself. This is suggested when he informs Uncle Grandpa and the others on how if Charlie Burgers goes through the black hole he will be sucked into a dimension where he will be ripped apart by tentacle monsters.
- Belly Bag didn't speak in a few episodes like the pilot episode, "Brain Game", "Big in Japan", "Future Pizza", "Bad Morning" and "Prank Wars".
- "Belly Bros"
- "Tiger Trails"
- "Space Emperor"
- "Funny Face"
- "Moustache Cream"
- "Driver's Test"
- "Uncle Grandpa Sitter"
- "Uncle Grandpa Ate My Homework!"
- "Uncle Grandpa for a Day"
- "Afraid of the Dark"
- "Treasure Map"
- "Locked Out"
- "Brain Game" (non-speaking role)
- "Mystery Noise"
- "Charlie Burgers"
- "Uncle Grandpa Shorts"
- "Perfect Kid"
- "Big in Japan" (non-speaking role)
- "Leg Wrestle"
- "Future Pizza" (non-speaking role)
- "More Uncle Grandpa Shorts"
- "Viewer Special"
- "Bad Morning" (non-speaking role)
- "Prank Wars" (non-speaking role)
- "1992 Called" (non-speaking role)
- "Bezt Frends"
- "Food Truck"
- Hide and Seek
- The History of Wrestling
- "Slice of Life with Pizza Steve" (non-speaking role)
- "Fishing with Uncle Grandpa"
- "Tiger Talk" (narrator)
- "Uncle Grandpa Changes a Light Bulb" (non-speaking role)
- "Tiny Miracle the Robot Boy" (non-speaking role)
- "Uncle Grandpa Sings the Classics" (brief cameo, non-speaking role and mentioned in songs)
- "Uncle Grandpa Story Time Storybook of Stories: The Legend of the Beardman - The Nighttime Tickler" (non-speaking role)
- "UG Rap Attack"
- "Board Game Night"
- "Uncle Grandpa Cooks a Burrito"
- "Shave Time"
- "Ghost Math"
- "Moments in History with Mr. Gus"
- "Bubble Trouble"
- "What's cookin', good lookin"
- "HOW COULD YOU?!?!"
- "What Uncle Grandpa is trying to tell you is that we didn't invite you because you never seem to find anything funny, Mr. Gus!"
- "Uncle Who-AUURHGJFGDGSKJDF"
- "I know we're gonna die a horrible death and all, but I can't help but feel worse that we hurt Mr. Gus' feelings!"
- "We're not being weird, Mr. Gus, it's who we are!"
- "FOG MACHINES?!? *coughs* MY FAVORITE!!!"
- "BUT WHAT ABOUT OUR MYSTERY DATES?!"
- "Boy, oh, boy! This sure is fun!"
- "Sounds fun... no, WAIT! I WAS BEING SARCASTIC!"
- "Please don't go through my web history!"
- "Oh yeah! I keep them right next to my unicorn stables and hamburgers in a jar."