The story begins with Drake and Josh in the living room. Megan walks in and sets off a switch, and the boys are covered in mashed potatoes. The boys say "Megan!" before wondering how to get her back. Just then, Uncle Grandpa pops out of the TV and says "Good Morning" before seeing the boys trapped in the mashed potatoes. Drake and Josh ask who he is and he says "I'm your Uncle Grandpa" and belly bag says he's not just their Uncle Grandpa, he's everyone in the world's Uncle Grandpa, "and when he comes to visit, you're sure to have a fun time". Josh thinks that's pretty cool, and Drake says he wishes he and Josh could get back at their sister. Uncle Grandpa understands and says he was quite the pranking scoundrel back in his day, and offers to help. Later, the three enter Megan's room while he's away at band camp. Uncle Grandpa says they need something she won't see coming, then says he has the perfect idea. Later, Megan returns, and Drake, Josh, and Uncle Grandpa, who are hiding under her bed, press a button, and the room suddenly turns into a fiery inferno, and Slayer's "Dead Skin Mask" plays in the background. She then sees a giant demonic version of her hamster, who says he heard Megan was very naughty towards Drake and Josh, then tentacles drag Megan under, then a giant, eight eyed monster appears and swallows her up. Later, she finds herself back in her room, where giant versions of Drake and Josh stare her down, then melt and turn into a demonic version of Uncle Grandpa, which laughs evilly. Megan then runs out of her room, swearing never to prank Drake and Josh again. The demonic version of Uncle Grandpa then fades to reveal Drake, Josh, and Uncle Grandpa, who high five on giving Megan the biggest scare of her life. Uncle Grandpa bids them farewell as he goes through his checklist of kids to help (all of which are characters from different shows) as he makes his way to Carly from iCarly to help.