This was Ricardo Montalban's first film since The Naked Gun: From the Files of Police Squad! (1988) 14 years earlier. He only appeared in television not movies during the intervening years.
Second film shoot entirely using High Definition Progressive Scan Digital Camera. Director Robert Rodriguez bought 2 digital cameras after comparing digital vs. film.
Carmen calls for "rebreathers" in the Drangonfly sub. However, when she and Juni are swimming, they release bubbles associated with standard scuba respirators. Rebreathers recycle much of the gases in the system, reducing or virtually eliminating bubbles.
When "falling" into the volcano, Carmen asks Juni how long they have been falling and he guesses "about 3 hours". He should have known that they couldn't have been actually falling for that length of time as it would only take 42 minutes to fall right though the Earth.
In the party scene, when all the metal objects are flying up to the magnet, you see china plates going up too. However, in an agency like the O.S.S., it's just possible that the plates are actually metal objects (such as weapons) disguised as China plates.