1. Chi Chi should be pregnant with Goten (I'm not saying she wasn't) and should show signs of it.
2. Trunk's hair.
3. The fact that the time machine takes a long time to recharge.
4. Gohan's power (I think it's stated that Bojack is as strong as Cell (or more) and, as we all know, Gohan doesn't train after the battle with Cell. So, if the movie would take after 1 or 2 years after Cell, Gohan's power would be weaker.
Movie 13 should include Buu. He would have been defeated pretty quickly, but he would show up, no matter what.
EDIT: Oh boy, we went waaaay off-topic. I had to check what was the subject of this thread.
The Bardock special states that only one baby was born in that day. Raditz is older than Goku (and obviously a low-class warrior) so he might have been sent to a planet with weaker ppl before Freeza destroyed planet Vegeta. Also, in a personal translation of what Raditz says in the Japanese version of episode 2, it is implied that he and Nappa were together in the same planet when Vegeta exploded (the planet
The thing with Tullece and the resemblance with Goku is also explained in the movie's tankoubon in the little section explaining who the characters of the movie are and what are their relation.

