Just after the battle with Obi-Wan, Jango Fett jumps onto his ship, the Slave 1. As he enters the ship, he hits his head on the door. It could be an intentional reference to the Stormtrooper that hits his head on a door in Episode IV (a famous error from the series).
Actually, Jango does not hit his head on the door. But in fact ducks so he will miss the painful blow. This is easy to belive that Boba would close the door in such a hurry not relizing his "father" is on board yet, becasue after all there is a Jedi after them.
Sorry, Jeff. But, George Lucas's official star wars homing beacon says that Jango Fett bonking his head's an egg not a slip-up. It says:
It appears that Fett genes and low headroom don't mix. In an homage to the classic Star Wars misstep, wherein a stormtrooper bangs his head on a low-hanging door, Jango Fett also takes a wallop on the noggin -- complete with sound effect -- as he enters the Slave I after tangling with Obi-Wan.