Lil' Mac is the 18th episode of Uncle Grandpa Season 4, and the 122th episode overall of the series.
Mr. Gus's nephew terrorizes Uncle Grandpa and Pizza Steve.
The RV is parked in a yard, Mr. Gus wants the guys to meet his one and only nephew Lil' Mac, Mr. Gus calls for Lil' Mac to come out from behind him and he pokes his head out. Pizza Steve and Uncle Grandpa are amazed at Lil' Mac and they introduce themselves to him, Uncle Grandpa wants to know what special activities they have planned today, Mr. Gus figures that the yard needs work so he thought they can tag team some outdoor chores and show them why the Gus family has green thumbs, Lil' Mac sneezes and Mr. Gus informs them that Lil' Mac has allergies and can't help his uncle Gus. Mr. Gus doesn't know what he's going to do as he promised his sister that he'll watch over Lil' Mac for the day, and he can't leave the yard in that condition or they'll get a write up from the HOA, Uncle Grandpa offers to watch over Lil' Mac while he does the yard work and Pizza Steve says that he can teach him how to be just like him. Mr. Gus says that'll be great and wonders if they can handle the responsibility, Uncle Grandpa tells him that they're professionals, Mr. Gus tells them that he owes them one and he fist bumps Lil' Mac and heads out to do yard work, Uncle Grandpa tells him that they got him covered and Mr. Gus is grateful to have them as friends.
Uncle Grandpa decides to give Lil' Mac a tour of the RV and Lil' Mac starts to destroy the TV, they stop him and Uncle Grandpa takes away Lil' Mac's bat and wonders where he got it, Pizza Steve comes back with a hammer and Lil' Mac starts to cry. Mr. Gus enters the RV and sees Lil' Mac crying and says WHAT THE HECK IS GOING ON IN HERE, IS EVERYTHING OK! real fast, Uncle Grandpa tells Mr. Gus that they're just doing kid stuff and that there's nothing to worry about. Mr. Gus is angry to catch them with a bat and a hammer and Lil' Mac crying and there's nothing to worry about! Uncle Grandpa and Pizza Steve try to explain what happened and Mr. Gus doesn't believe that story and that no nephew of his will do such a horrible thing and asks Lil' Mac if he's right, Lil' Mac smiles with a halo over his head. Mr. Gus tells them to play nice with Lil' Mac and to look after them like responsible adults, tells them that they're better than this and closes the door.
Uncle Grandpa, Pizza Steve and Lil' Mac are sitting together with a toy box, Uncle Grandpa explains that all good little boys like to play with little toys, he then chooses a toy from his prized collection which is his limited edition Weird Man action figurine, he states that only 40 of them were ever made and hands it to Lil' Mac. Lil' Mac opens the furnace, Uncle Grandpa and Pizza Steve start to panic as he puts the figurine in. Uncle Grandpa cries and Pizza Steve scolds him about destroying Uncle Grandpa's favorite toy and tells him if he has no moral code, Lil' Mac begins to cry, but they stop him before Mr. Gus can hear it. Uncle Grandpa figures that they should stop him from crying, Pizza Steve asks Belly Bag for something and Belly Bag hands them a new tiny turtle neck sweater, Pizza Steve puts it over Lil' Mac. Uncle Grandpa picks up Lil' Mac and tells him that his reign of terror has come to an end, he opens a window and tells him that they can't have a little devil wrecking the RV and he puts him in a pot on a shelf as a timeout, and Uncle Grandpa takes out the trash since it's trash day.
Uncle Grandpa and Pizza Steve are relaxing on the couch without any worry of Lil' Mac, Mr. Gus pops up from the window and wants to know where is his little angel and he doesn't see him, Pizza Steve says that he's taking a nap in Uncle Grandpa's bed, Mr. Gus thinks that Lil' Mac is tuckered out and continues to finish his yard work. Uncle Grandpa thinks that it was some good thinking of Pizza Steve and that Mr. Gus would be mad of them if he found out Lil' Mac is in a timeout, Pizza Steve worries that Mr. Gus will come back any second now and Uncle Grandpa tells him to calm down and that they have to get Lil' Mac before Mr. Gus gets back. Uncle Grandpa opens the window and sees that Lil' Mac is not there, Pizza Steve figured that he must have landed in one of the trash cans, they see Mr. Gus taking the trashcans away. Uncle Grandpa and Pizza Steve panic because Lil' Mac is in the trashcan, Uncle Grandpa worries that Lil' Mac is in the trash can, Pizza Steve tells Uncle Grandpa that they just have to wait for the perfect time to get Lil' Mac. The two then sneak around the RV and Mr. Gus notices them and wonders what are they doing out there, Uncle Grandpa tells Mr. Gus that he forgot a bag of lawn trimmings and he goes to get it, Mr. Gus then goes to the trashcans and apologizes for giving them a hard time with Lil' Mac and owes them a deep debt of gratitude. Before Mr. Gus opens the trash can, they try to tell him not to do it as they worry he might see Lil' Mac, Mr. Gus then notices to put the bag in the green garbage can. Mr. Gus tells them that he's going to go wash up and then they can get Lil' Mac back to his sister, he tells them to wake him up and he goes inside.
Pizza Steve tells Uncle Grandpa to hurry and get Lil' Mac out of the trash and out of their lives. Before Uncle Grandpa can open the garbage can, the garbage truck arrives and takes it and Lil' Mac is thrown in, Uncle Grandpa tells Pizza Steve they have to do something and he worries that they won't catch him in time on foot, Uncle Grandpa's foot then transforms into a car and they head out for Lil' Mac. They come close to the garbage truck and the light changes, the garbage truck then gets away, Uncle Grandpa tells him the light will change until a electrician puts an out of order sign on the light. Uncle Grandpa and Pizza Steve panic all the way back to the RV, Pizza Steve can't believe that they lost him, Uncle Grandpa doesn't want to think about what Lil' Mac must be going through, and Pizza Steve doesn't want to think about what Mr. Gus will do to them when he finds out what happened. Mr. Gus walks into the RV and wants to know where's Lil' Mac, the two begin to cry and Mr. Gus gets suspicious as he calls out for Lil' Mac, he tells them it's not funny if his sister calls. The phone begins to ring and Mr. Gus picks it up and talks with his sister Becky, they're talking about Lil' Mac and the guys begin to cry, Mr. Gus is happy and he tells them that he owes them one.
Uncle Grandpa and Pizza Steve are in shock for a whole day, Mr. Gus opens the RV and asks them for round two. Uncle Grandpa and Pizza Steve sees Lil' Mac running from the garbage truck and they're happy to see him as he pounces on them. Becky thanks Mr. Gus for watching Lil' Mac again, he couldn't stop talking about how much fun he had yesterday, Mr. Gus tells her no problem and that they're great with kids, Becky will see him again after her double shift and Mr. Gus tells her to take her time and he'll see her tonight.
- This episode's quote is "What's that terrible sound?"
- Lil' Mac's has the same name of the "Punch Out" character Little Mac.
- In this episode, the RV acts like a house with it inside a yard just like in A Gift for Gus, the RV also has garbage cans in the back.
- In Dinosaur Day, Uncle Grandpa said that the meteor wiped out all his family and friends, where there are still known relatives of Mr. Seen in this episode.
- There's a toy in Uncle Grandpa's collection that resembles "Captain America".
- Uncle Grandpa's favorite toy was the Weird Man limited edition action figurine as only 40 of them were ever made.
- Uncle Grandpa's foot can change into a car, this is a possible reference to "Turbo Teen" where a teenager has the ability to turn into a car.
- Running Gags:
- Lil' Mac sneezing on Pizza Steve.
- Lil' Mac destroying something.
- Lil' Mac crying.
- Mr. Gus doing yard work.
- The teeth and the rake Mr. Gus is holding has the ends connected to the rake.
- The RV shows a smoke chimney when Lil' Mac destroys Uncle Grandpa's toy, it's only there for that part of the episode.
- Uncle Grandpa is driving his foot car, when his leg was connected to the back of he car.