Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a Hong Kong action movie/comedy starring Jet Li. It's a parody of Die Hard and of Jackie Chan's movies among other things, but it's still full of a lot of stupid action cliches that I don't think are meant to be funny - "do I cut the red wire or the blue one to defuse the bomb?"
Basically, Jet Li plays the bodyguard and stunt double for a huge Hong Kong action star (a parody of Jackie Chan and also Bruce Lee.) They become accidentally involved in a jewel robbery in a skyscraper when a large gang of vicious terrorists break into a gala party and take everybody hostage while they try to hack into the cases full of precious jewels. One of the hostages is a woman TV news reporter. At one point she escapes from the group of captives and hides in a rest room, but one of the terrorists finds her there and starts pulling snakes from a bag and throwing them at her. (The terrorists must have brought along bags full of deadly snakes along with lots of automatic weapons and bombs and even a flame thrower, so they would be prepared for anything.) He throws snakes at the reporter as she stands on a toilet and threatens her to give him the videotape she made of the leader of the gang. Then, as most stupid henchmen in stupid action movies do, he says he'll be back in 5 minutes and leaves her alone to think about his demands. That's enough time for her friends to break through the ceiling and pull her up to them. But before that she sees a large monitor lizard that must have also been tossed out of a bag by the terrorist. When she jumps up to the ceiling the lizard jumps down and lunges at her, but misses. After she is safe above the ceiling, the movie star accidentally falls out of the ceiling and the lizard leaps up and bites him on the butt. He is pulled up and tosses the lizard down. Later he is worried that he might have been poisoned and we see bite marks on his underwear. His father sees Jet Lee cut and suck a snake bite on a woman, then tells his son he's not going to suck the poison from his butt.
I think the lizard is a Savannah Monitor, a native of Africa.