Somebody had the great idea to cast Seth Rogen as the nerdy estranged son of doting Jewish widow mother Barbra Streisand. That person might want to rethink his/her future in the movie biz.

The Guilt Trip is an instantly forgettable film starring two people who have little chemistry. A weak and rarely funny script from a flimsy story idea doesn’t help. Did producers think that when these two appealing stars got together before the camera that magic would just spontaneously happen? Well, it didn’t.

Rogen plays a 30-ish LA chemist who flies back to Jersey to visit his mom before driving back west with stops along the way to pitch the cleaning solution he’s developed. A story his mother tells inspires him to invite her to make the week long trek across America with him.

Things that could’ve been funny are not, such as the choice of a book on CD they listen to in the car. Or Rogen’s uninspiring sales technique. Even the challenge at a Texas steakhouse to consume a monster chunk of meat in one hour produces little in the laughter department. Even the “hilarious” outtakes that run during the closing credits are ho-hum.

Much of the blame for The Guilt Trip’s failure goes to the old pro, Streisand. First, she’s had so much work done that she doesn’t quite look like Barbra Streisand anymore. Second, her character is only moderately wacky. Over-the-top zany might’ve worked better. Dialing back the wackiness does allow for a few moments of sweet motherly sensitivity.

Rogen is a talented actor and writer, but he does better in R-rated movies than in this PG-13 film. (Despite its tamer rating, there is a penis joke. A lame one. The joke, that is.) His name and reputation will sell tickets, but The Guilt Trip will not add to his long-term box office appeal.

This is a movie to watch on an obscure cable channel in four or five years when nothing else is on. There are better films in almost every other theater in the multiplex. This is not a trip you want to take.