Uncle Grandpa for a Day is the 10th episode of Uncle Grandpa Season 1, and the 10th overall episode of the series.
After Uncle Grandpa and Belly Bag get stuck in peanut butter jars, it's up to Pizza Steve and Mr. Gus to help a young boy named Guillermo with his bike problems.
Uncle Grandpa starts off the episode by singing the I Love Peanut Butter song with Mr. Gus. Pizza Steve comes in an interrupts the song questioning who's turn it is to drive The UG RV. After making some deductions, they realize whoever is supposed to be driving isn't actually driving the RV. They all quickly run to the cockpit of the RV to find an empty jar of peanut butter on the seat with a note that says "Out of peanut butter, be right back" which is a huge indicator that Uncle Grandpa was supposed to be driving the RV. Everyone looks angrily at Uncle Grandpa before trying to control the RV and keep it from crashing. After missing a pedestrian and a car, the RV ends up driving off of a ramp that was set up. The ramp sends them up into space before is crashes back down onto a bicycle.
Unfortunately, the bicycle belonged to Guillermo, who was trying to ride it at the time. To make matters worse, the bicycle was actually brand new. Pizza Steve tells Uncle Grandpa that he needs to help the kid, but Uncle Grandpa has a peanut butter jar stuck on his head from the accident. Pizza Steve tries to ask Belly Bag, but Belly Bag also has a jar of peanut butter stuck to his face. Pizza Steve decides maybe it is best to help the kid another time, but Mr. Gus reminds him that if they do not help the kid the reputation of Uncle Grandpa will be ruined and they will lose everything. Pizza Steve does not want Uncle Grandpa to lose anything, so he helps Mr. Gus think of a plan to help the kid. They decide the best course of action is for Mr. Gus to pose as Uncle Grandpa and for Pizza Steve to pose as Belly Bag.
Mr. Gus comes out of the RV wearing Uncle Grandpa's clothes and wearing Pizza Steve like he would Belly Bag. He talks to Guillermo, who tells him about how his new bike is broken. Pizza Steve reassures the kid that they will get him a new one. Mr. Gus sternly pulls Steve aside and reminds him that they do not have the same powers as Uncle Grandpa and can't actually get him a new bike. Pizza Steve devises a plan to use a nearby garbage can as a new bike and just pretend it's a "magical Uncle Grandpa bike".
Pizza Steve tricks the kid into thinking a garbage can is actually a magical Uncle Grandpa bike, and with the help of Mr. Gus he pulls all kinds of crazy stunts with the garbage can to make it seem like it is magical. Guillermo totally buys into the lie and thinks it's a magical Uncle Grandpa bike after they show him how to "work it".
After fooling Guillermo, Mr. Gus and Pizza Steve begin to leave. As they leave, Guillermo informs them that he is going to ride his new Uncle Grandpa bike down Danger Mountain. When Mr. Gus hears that, he realizes the mistake they made and immediately chases after Guillermo. Guillermo is already on the top of danger mountain ready to roll down the hill. Mr. Gus comes running after him, but before he could grab Guillermo, the kid jumps off the cliff and begins to roll down the side in his "magical Uncle Grandpa bike". Mr. Gus rolls after him. They all end up rolling off the edge of the cliff and begin to free fall down.
Mr. Gus is about to confess how dishonest him and Pizza Steve were being until Uncle Grandpa came riding in on Giant Realistic Flying Tiger. He tells them he escaped the peanut butter jar by chewing his way out and then reveals the garbage can actually has the time travel feature Pizza Steve supposedly made up when telling Guillermo how the "bike" worked. Uncle Grandpa reverted the time back to when the accident started. Before the RV could crash down on Guillermo's bike, Mr. Gus moved the bike over so the RV would just crash onto the pavement.
The UG gang walks back into the RV in doubles. Guillermo also has a double, and waves goodbye to the UG gang doubles before being weirded out about having a doppelganger.
- The Crazy Baby, Beary Nice, Hot Dog Person, Tiny Miracle, Charlie Burgers, and Frankenstein are in the title card.
- When Guillermo said "Wait, there's two Uncle Grandpa's?" and Mr. Gus said "Yeah, it happens." That was a reference to the way Uncle Grandpa always makes clones of himself.
- This is the first episode where Uncle Grandpa has a minor role.