''Look Who's Talking Too'' proves that you shouldn't let success go to your head. It proves, rather conclusively, that you shouldn't go back to the cameras before you are prepared to do so, before you have any idea of what you hope to do.
''Look Who's Talking Too'' is the sequel to the supremely successful ''Look Who's Talking,'' the comedy that gave John Travolta a needed career boost. The sequel won't nullify all that, but it certainly won't help. With this one, Travolta may be back to, well, square two.
''Look Who's Talking'' was a charmer, a novelty in which a child, with the voice of Bruce Willis, spoke before and after his birth, while his mother took up with a cab driver who wanted to be a pilot.
The sequel is . . . well, not much. The new film is only 84 minutes long and, in truth, has one or two laughs, but for the most part fizzles before your very eyes. If there is a plot, don't look for it. The movie looks as though it was thrown together, made up on the spot, scene for scene, by director Amy Heckerling and the scriptwriters (using the term very loosely), Heckerling and Neal Israel.
Kirstie Alley re-teams with Travolta, and this time they are married and bickering. That's really all the film is, bickering between the principals and the kids. In the first film, there was only the boy. Now, he has a sister, spoken for by Roseanne Barr.
You don't want a kid with a voice like Barr's, but she does help. Her unique intonation gives life to lines that don't really have any.
There is a lot of talking among the kids, brother, sister and friend (they meet him at the playground) with voice by Damon Wayans of television's ''In Living Color.''
Most of the kids' conversation, however, has to do with bathroom business, pooh-pooh talk, and at one point the toilet actually talks back, voice by Mel Brooks.
That's about as good as things get in this film, save for one scene in which Alley pelts a construction worker with groceries.
Elias Koteas plays Alley's brother. He's supposed to be a gun-happy right winger. He's about as funny as the rest of the movie.
''Look Who's Talking Too,'' in which the husband and wife are more tiresome than appealing, means to be no more than v vTC sketchy collection of laughs. It's sketchy, all right.
The new film is showing at local theaters. The best thing about it is the final background number, ''I Got You Babe,'' as sung by Sonny and Cher. That's worth hearing. The rest is quickly forgotten.
''Look Who's Talking Too''
* The continued adventures of the kid who talks like Bruce Willis and his parents who mostly bicker with each other.
CAST: John Travolta, Kirstie Alley, Olympia Dukakis, Elias Koteas, Twink Caplan, Bruce Willis, Roseanne Barr, Daman Wayans, Mel Brooks
DIRECTOR: Amy Heckerling
RATING: PG-13 (sex, language)
RUNNING TIME: 84 minutes