One year after the Diary of a Wimpy Kid: Dog Days (film), while at the Corny's family restaurant, the Heffley family — consists of Greg Heffley, Rodrick, Frank, Susan and Manny — plans to take a road trip across the USA to attend Meemaw's 90th birthday. However, after Greg and Rowley rescue his younger brother Manny, who got stuck inside a tube in the play area, Greg ends up in a ball pit with a diaper stuck on his hand, startling him. He subsequently becomes famous after the people around him record him and post the footage on the internet, leading Greg to be dubbed as "Diaper Hands", much to Greg's devastation.