Greg Heffley is a 12 year old who is fresh out of elementary and transitions to middle school, where he has to learn the consequences and responsibility to survive the year.

The Heffley family attends a party at a roller rink, where Greg Heffley reunites with his best friend List of Diary of a Wimpy Kid characters#Rowley Jefferson, meets a new girl at school named List of Diary of a Wimpy Kid characters#Holly Elizabeth Hills who Greg instantly has a crush on, and reveals he passed on the Cheese Touch. During the party, his older brother List of Diary of a Wimpy Kid characters#Rodrick Heffley advises Greg to ask Holly to skate with him when Couples Skate begins and then interferes with Couples Skate by persuading a crowd of hooligans to enter the rink, along with replacing "Always (Atlantic Starr song)" by Atlantic Starr with a heavy metal music song. This prompts Greg's parents, List of Diary of a Wimpy Kid characters#Frank Heffley and List of Diary of a Wimpy Kid characters#Susan Heffley (who misunderstand this) to speak to Greg on the rink's public address system and then carry him off the rink. Greg, extremely angry with Rodrick for humiliating him, tries to tackle him, but he misses and in turn, lands in a little girl's birthday cake. She and her friends then furiously proceed to beat up Greg as the intro starts.

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.