Jar-Jar and C3PO, Actors Make a Cameo
In the scene where Anakin and Kenobi follow Zam into the club there are two Coruscant security officers who aknowledge the Jedi's presence. These officers are no other than Ahmed Best (Jar-Jar Binks) and Anthony Daniels (C-3PO).
George Lucas and Rick McCallum Make a Cameo
In the Senate room after Jar-Jar has suggested to give Senator Palpatine special powers to create a grand army of the republic, there is a scene where senator Palpatine has accepted the power. After that, we see the camera move past a group of "Greedo" creatures. If you look carefully, you will see on the platform below the "Greedo" creatures, George Lucas and Rick McCallum are applauding.
George Lucas' Kids Make a Cameo
George Lucas' two children make a cameo in the move. His daughter appears first, in the bar where Anakin follows Zam. She is the woman with the two tendrils on the back of her head that watches Anakin pass. The second appearance is the scene that takes place in the Jedi Library. The boy that talks to the librarian after she is done helping Obi-Wan is George Lucas' son.
Java the Hutt?
In the credits, there is a character named "Java The Hutt" but there was no such character in the film. The person given credit, Michael Smith, is actually the guy who got coffee for the cast and crew during filming.
Just before Anakin leaves the Lar's homestead to find his lost mother, he is standing next to the domed entrance to the dwellings. Padme comes up the stairs, calls his name and as he turns, the shadow cast on the wall is that of Darth Vader. (Note - Some argue that this is not the shadow of Darth Vader but a coincidence and the real shadow of the actor).
1138, the infamous reference to George Lucas' first movie (which appears in virtually every film Lucas has worked on) can be found near the end, in the scene where Lord Dooku is flying away from the fight. The droid which is flying the ship says it aloud.
Millenium Falcon Spotted
When the transport ship carrying Padme and Anakin arrives at the Naboo starport, look at the bottom left of the screen. Slightly above the corner you will see the Millenium Falcon sitting on the landing pad.
Qui-Gon Makes an "Audio" Appearance
In the scene when Yoda is meditating, right after Anakin kills the Sand People, you hear Qui-Gon yelling: "Anakin! No!" This may be the first time a Jedi has returned from death which might explain why Qui-Gon did not vanish at the end of Episode I (as the other Jedi did in the original trilogy).
Jango Takes a Hit to the Head
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.
X-Wings & Tie Fighters?
Star Wars continuity purists will have a hard time explaining just how an X-wing fighter and TIE fighter got into the speeder chase over Coruscant.
Skywalker Sound Logo
In the end of the Coruscant speeder chase, Obi-Wan arives at the bar club where he meet Anakin, just when Obi-Wan lands his speeder, you can see the Skywalker Sound logo rotating in the background.