Continuity: When Jason's sister's boyfriend arrives, he clearly switches off his engine and removes the key, but the sound of the engine can still be heard. When he gets in the car again, the keys are in his hand but the engine is still running.
Continuity: After the car is supposedly smashed by the monster truck the mag wheels are different when it is being towed.
Factual errors: The headline in Variety uses the word "Prez" to refer to the new president of the studio. Variety would always use "Prexy", not "Prez".
Continuity: When Marty gets ready to go swimming, he hits a switch to turn on the music. The switch is shown both "on" and "off" after that.
Continuity: When Kaylee gets stuck on the Velcro wall the position of her body, (most notably her height) continuously changes between shots.
Continuity: When Jason finishes writing his story "Big Fat Liar", he staples the papers together, but when Marty Wolf picks it up in his limo, the papers are not stapled. Also, the writing of the title "Big Fat Liar" looks different from when we see Jason writing it (especially the "i" in "liar").
Crew or equipment visible: Crew members and lights are reflected in the blue dye bottle as Jason is pouring it into the pool.
Boom mic visible: In the classroom in the beginning, the boom mic is clearly visible for a significant amount of time.
Revealing mistakes: When Marty tackles Jason on the roof for Mr. Funnybones, after Jason falls, the ground moves revealing a crash mat.
Continuity: In the scene where Wolf realizes his car has been sabotaged (specifically where he finds that his brakes are connected to the car horn), his brakes clearly work as he stops his car (despite hearing the car horn when he hits the brakes) but in the scene immediately following we see he cannot stop the car, as it should have been in the earlier scene.
Continuity: When Jason crashes into the limo you can clearly see the damaged bicycle. After Marty agrees to give Jason a lift and he goes to get into the limo, the bicycle is gone.
Continuity: During the movie premiere Jason's dad puts his hand on Jason’s shoulder and says something. You can see Kaylee sitting on his left. Then it zooms out and she is sitting on his right.
Revealing mistakes: Jason Shepard liberally applies a super glue-type product to the earpiece of Wolf's cell phone hands-free set. Any type of super glue product should dry pretty quickly after it's applied. Wolf finished swimming and took a shower as well as freaked out when he saw himself. By the time he stuck the ear piece into his ear, the glue should have at least been tacky if not dry. It would have been "easily" removable.
Continuity: When Marty Wolf swims in the dyed pool, all of his skin turns blue yet his bathing suit remains it's original color.
Continuity: When Jason puts the super glue on Mary Wolf's earpiece, it certainly would have dried long before Marty put it in his ear. It would not have gotten glued in his ear.