A 15-year-old boy named Jack Parker has everything going for him: popularity at school, an easy home life, and a high chance of winning an award that would lead him to be bat boy for the Boston Red Sox. There's just one thing; he earned them by being the biggest liar around, he didn't realize that all was going to change one day while he was giving a speech on a school news report. Mikey, one of his lies, appeared. Progressively, one by one, all his lies started to come to life: two angry lumberjacks and a possessive, jealous girlfriend from Arizona.
Jack and his friend talk to a plush purple hippo from a children's restaurant/fun center, and they find out that the only way to stop his lies from coming true is to tell the truth. He refuses to do it since the award ceremony was coming soon and didn't want to lose.
After that encounter, they soon faced the lumberjacks along with another one of his lies: two alien agents. They were able to escape with the help of the girlfriend, but only after he told her the truth. During this time (and a few more lies later), Jack learns that his lies mostly hurt those who are closest to him (especially those who are supposed to protect and love him).
After a conversation with a man practicing his baseball hits (who Jack later actually finds out is his baseball hero, Danny Kostas, getting over a slump), Jack admits to everyone in the award ceremony about the lies that he told, and was disqualified as a result. He and his friend soon saw all of his lies in the hall, and ran into an empty room, where they saw the hippo.
After Jack tells the hippo that he told the truth and none of lies went away, the hippo revealed itself to be his sister Hannah, who was fed up with his lies and wanted to teach him a lesson; she revealed that the lies were just actors and other people using special effects, and that they rehearsed the plot for months. They soon reconciled. Then his parents came in, angry, and grounded Jack by making him clean the whole garage. In the end, Jack manages to clean the whole garage, having learned his lesson about lying.
He then visits Jennifer, the girl that he has a crush on, so he can apologize and promise he would never lie again for now. They soon take off in a limo to Red Sox Stadium, complementary of Danny.
- Bradley Steven Perry as Jack Parker
- Brittney Wilson as Hannah Parker
- Tyrel Jackson Williams as Mikey
- Harrison Houde as Kyle
- Nicholas Coombe as Eric
- Eduard Witzke as Ride Operator
- Rachelle Gillis as Lisa