Revealing mistake: Right after they "create" Leeloo and she is lying in the plastic cage with the little straps on her, the guy approaches her and says, "if you want out, you are going to have to work on your communication skills." She gives him a dirty look, and then you can see a huge hole, pre-cut in the glass, that she busts her hand through. (00:29:47)
Revealing mistake: When Korben Dallas "negotiates" with the Mangalores by shooting their leader in the head, the small tube used to create the hole in the leader's head is visible.
Revealing mistake: When the space ship leaves the Earth's atmosphere about to make the jump to Phloston Paradise, you can see the box around the spaceship used as part of the effects process.
Revealing mistake: When the doors of the temple close on the Mondoshawan, it shakes like styrofoam.
Revealing mistake: When the bomb that Korben puts on the balcony explodes, there are two quick shots of the Mangalores. They are dummies because they've stopped shooting and don't move. (01:42:10)
Revealing mistake: When Zorg is talking on the phone with Mr. Shadow, a tube is briefly visible on his forehead. It is used to deliver the brown "goo" onto Gary Oldman's head a few seconds later. (01:16:30)
Revealing mistake: Whilst Diva Plavalaguna is singing, you can see the back of her head creasing and bending. This is because the suit that the actress is wearing is made out of foam latex; confirmed by Nick Dudman, Creature Design Supervisor on the DVD featurette "An Audience With Diva Plavalaguna".
Revealing mistake: After Korban meets Ruby and everyone leaves them alone, Korban grabs Ruby by the neck and holds him to where his feet can't even reach the ground. In the first shot, you can tell that Korban's hand isn't even applying pressure. In the next few shots of Ruby, still being held off the ground, you can now see that Korban's applying a little pressure now, but probably not as much as there should be while holding a full grown man a foot off the ground.
Answer: I looked it up and it is Jill Milan. If you do a search for her, it is in her credits as an actress.