This is a visual effect where a shot is ended by having the camera zoom into a character's wide open mouth, usually while this character is screaming or singing. Usually done in animation, since, among other things, it's likely to be a Gross Up Close Up in live action. Also done in commercials. Sometimes, it is done to represent something literally entering a character's mouth; usually, however, it is solely a visual effect (similarly used with eyes and noses).