Pete sticks Velcro onto a girl's diaper and a table to stop her running away in the photo shop. When Goofy offers her a toy at one point, the Velcro square is not seen; yet when she runs away, leaving her diaper on the table, the Velcro square is visible again.
As Max and Goofy are floating over the waterfall, Goofy falls when the handle of the fishing rod slides off. As Max performs the "perfect cast" to save him, the handle is back on the rod, then it is off again afterwards.
The position of Goofy and his tent changes in relation to Pete's giant RV. At first the RV stops so that Goofy is directly under the midpoint, then after it sets up the tent is peeking out the back. When the door opens the tent is completely under the RV.
When Goofy and Max arrive at Roxanne's house after the Powerline concert, Max is sitting in the car with his seat belt on. When he is getting out of the car you can still see the seat belt over his shoulder but he gets out of the car without ever taking it off.
During the "After Today" scene when the school bus drives by, Bobby can be seen sitting directly behind the two girls dressed in black. Then when the inside of the bus is shown, it is filled with cheerleaders. Then when the bus arrives at school, Bobby can be seen again getting off the bus.
Goofy's car door handle is seen throughout the movie as being both vertical and horizontal. There is also a keyhole in certain scenes, but not when Goofy goes to unlock the door with his key (after the Possum Park).
When Max gets frustrated at his father after the Lester's Possum Park, he tries to get in on the driver's side, but it's locked. However after Goofy unlocks Max's door, he opens his door without ever needing to unlock it.
When Bobby, PJ, and Max are getting ready for the Power Line gig, PJ is seen holding the camera as he tries to get the cable off of his foot, causing him to trip. When you see him fall through the curtain behind Principal Mazur, he is no longer holding the camera.
During "After today" when we see Roxanne walking past Max her reflection can be seen in the window. But her reflection has a mole, and it's the right side of her face that would be reflected in the window. And she only has a mole on the left side of her face.