George Clooney's scenes were shot in one afternoon in his own living room, in a suit jacket, shirt, tie and pajama pants.
Due to filming schedules, many of the actors playing characters in the final scene were never on the set at the same time and were put together digitally.
Steve Buscemi only agreed to make a cameo in the film if Robert Rodriguez personally assured him that he would be able to keep Sporky the flying pig after production was complete.
Prior to the film's release, it was originally announced that this would be the last Spy Kids movie, as the young actors, in particular Alexa PenaVega, were growing out of the role. However, Spy Kids 4: Tout le temps du monde (2011) was released, featuring Alexa Vega and Daryl Sabara in supporting roles.
Elijah Wood: Robert Rodriguez wrote the role of 'The Guy' with him in mind. Wood had previously starred in Rodriguez's The Faculty (1998) shortly before finding out about Le Seigneur des anneaux : La Communauté de l'anneau (2001). The suit that Wood wore was originally one for the character Juni, but they spray-painted it silver and Cellotaped it to him as it barely fit. In the shot where Wood is kneeling down, talking to the others, he is actually looking at the ground to give the impression that he is towering over everybody.
Rocket Rodriguez: The son of Robert Rodriguez can be seen when Juni walks into OSS, shortly after discovering what happens in "Game Over".