This story takes place in seventh grade.
The movie starts out with the Heffley family going down to the Christmas tree. Greg's mum starts going through what will be happening. She says that the guests are going to come at 1:30 then they will go out to play some sport (Soccer, Tennis, Wrestling, Swimming and get the kids to make up a sport.). Once they come home, loaded diaper will do a performance then everyone will unwrap their presents and sing Christmas carols. Then she reveals that she has invited some mystery guests. She says that Manny's mystery guest is Wesley, Greg's are Fregley and Patty Farrell and Rodrick's mystery guest is Heather Hills. She says that the reason Greg has 2 mystery guests is because he has been a very good boy.
Once everyone has arrived and they are at the soccer field, they play soccer, the teams are Greg, Susan, Manny, Wesley, Fregley and half of loaded diapers band V.S everyone else. Patty keeps kicking Greg in the balls and saying it's an accident, she starts to do it more and more with each sport because every time she does it, she gets a lolly from Susan to make it up to her for feeling guilty (She keeps faking being sorry and guilty.). Her sport that she makes up is basically tackling, Greg gets tackled by everyone (Even Manny and Wesley.).
Loaded Diaper's gig is a complete disaster. Patty gives Greg a filled water gun, she says her and Susan picked it out, but when he tries to squirt it, milk and flour comes out of the wrong end and squirts him, Patty and Susan claim that it was a harmless joke, but what Susan doesn't know is that Patty put a very strong glue in it as well, Greg is furious. Patty tells Greg's parents that she is very good at calming people down, so she takes Greg into his bedroom so she can beat him up a bunch of times. Patty then notices some very sharp needles and some masking tape, she puts the masking tape all over her hand while folding it so that both sides stick. She then puts the needles on the tape. She finally puts the needles into Greg and acts like she is patting him on the back. Susan is very proud of Patty and rewards her with choc-chip ice cream.
The next day, Greg accidentally runs into Frank, knocking him over, Frank is mad about this and starts considering sending Greg to Spag Union Military School, although he can't find out what grade it starts.
Greg's dad's new-year's-resolution is to cut down on sweets, Greg's mum's is to start going to the gym, Manny was going to give up his pacifier for good (His didn't last a minute.) and Greg was going to help other people improve
Greg Heffley: Zachary Gordon
Rowley Jefferson: Robert Capron
Rodrick Heffley: Devon Bostick
Manny Heffley: Connor and/or Owen Feilding
Susan Heffley: Rachel Harris
Frank Heffley: Steve Zahn
Patty Farrell: Laine Macneil
Holly Hills: Peyton List
Chirag Gupta: Karan Brar
Fregley: Grayson Russel