The entire "aggressive negotiations" conversation during the dinner scene between Anakin and Padmé was ad-libbed by Hayden Christensen and Natalie Portman at George Lucas' request, due to his not being happy with the romantic dialogue he wrote for that scene.
Because he wanted to be able to identify himself during the colosseum scene, Samuel L. Jackson (Mace Windu) specifically asked George Lucas if he could have a purple light-saber. Lucas replied that Jedi light-sabers were only blue or green, to which Jackson said "Yeah, but I want a purple one." Lucas said he'd consider the request. Jackson says he didn't know how it would turn out until he went in for re-shoots, which is when Lucas showed him the scene containing his purple light-saber.
When Jango Fett gets into his ship after his fight with Obi-Wan, he bangs his head on the partially open door. This was intentional, and is a reference to a famous goof from Star Wars: Episode IV - A New Hope (1977), where a stormtrooper accidentally bangs his head on a door.
Like Ewan McGregor did in Star Wars: Episode I - The Phantom Menace (1999), Hayden Christensen made "light-saber noises" the first time he was handed one in rehearsal. After chuckling at the young star's antics, George Lucas informed him that they probably had people in Sound Effects who could do a better job in post-production.
During rehearsals and filming of Count Dooku's light-saber battle scenes, a small model of Yoda was used as a reference point for Sir Christopher Lee. The model, however, was slightly altered to have vampire fangs, to which Lee's amused response was "I will not comment on that. I didn't think you would do this to me, George!" The fangs were likely a joke at Lee's expense for his performance as Count Dracula in Horror of Dracula (1958) and several other Hammer Studios horror films.
Anthony Daniels: As a human customer in the bar, when Anakin and Obi-Wan hunt Senator Amidala's attempted assassin, visible just after Obi-Wan draws his light-saber.
Ahmed Best: He is seen as a human customer in the bar, into which Anakin and Obi-Wan follow the assassin.