When Gotenks's ghosts swarm and kill the dictator and his men, the dictator is wearing his hat when he lost it earlier.
When Goten and Trunks are fighting the dictator, there is a shot featuring them in their base forms when they were Super Saiyan in the prior shot.
When Super Saiyan 3 Goku goes up to blast fat Janemba, a single frame of Super Saiyan Gogeta kicking Super Janemba can be seen. These two characters are not introduced until later in the movie.