Continuity mistake: When Ren and Ariel join Willard and Rusty in fighting Chuck and his friends, Chuck says to Ren "Why don't you come down here." As he says this he makes a "Come over here" gesture with his hand. The shot is from behind him, but then when it switches in front of him his hand is already down by his side before he put it down in the previous shot.
Audio problem: When Ren has his cousins teach Willard how to dance, he and Woody watch and comment. At one point Woody says "Less hips" and Ren says "A little less". When Ren says this his mouth isn't moving.
Continuity mistake: When the main characters are dancing at the drive in, Ren makes his way over to Ariel and dances while she is leaning on a car hood. When he gets to her the shot shows what's behind him (slightly at an angle) we see Chuck sitting up on his truck bed. When the shot changes to show his reaction he is leaning back, then sits up.