For as long as there have been movies, the chemistry of movie stars has been perhaps the most vital quality in whether a movie is a hit with audiences. Whether an audience is rooting for a couple to get together in a rom-com or deciding whether to cheer for a couple of heroes, the way stars interact onscreen is key to enticing viewers to suspend their disbelief and get involved in a movie's world. 
 
Two new movies show how chemistry or the lack of it can make a movie sink or swim. "Passengers" stars Jennifer Lawrence and Chris Pratt and is boring disaster, while "Why Him?" starring James Franco and Bryan Cranston offers more cheer to fans of R-rated comedies, but is highly questionable in terms of morals and taste.

"Why Him?" has distinctly earthbound plotting but soars to more entertaining heights than that failed space epic. The movie stars the unlikely team of Emmy-winning actor Bryan Cranston – whose lead turn on "Breaking Bad" has led to his being considered one of the best TV actors ever – and the Oscar-nominated goofball James Franco. 
 
Cranston plays Ned Fleming, a conservative printing shop owner from Grand Rapids, Michigan, who takes his wife Barb (Megan Mullaly) and son Scotty (Griffin Gluck) to California for Christmas after their 22-year-old daughter Stephanie (Zoey Deutch) invites them out so they can meet her new boyfriend. They don't realize that that boyfriend happens to a 32-year-old, oddball video-game tycoon and zillionaire named Laird Mayhew (James Franco).
 
One might think a couple of traditionalist parents would be delighted to find their daughter getting serious with a wealthy man, but Laird is covered in tattoos (including images of Stephanie's face on his left pectoral and of the Fleming family Christmas card on his back). He also is utterly uncensored, and shocks her parents with his comically incessant swearing and inappropriate comments to the point they want to run for their lives on the first night. 
 
Laird wants to propose to Stephanie on Christmas, and asks Ned for his blessing. Ned doesn't want to give it, but agrees to let Laird have a chance to start over and make a good impression over the course of the visit. Laird's culture-clash efforts to make good on his opportunity spark the rest of the movie's manic misadventures and risqué repartee. Mullaly and Keegan-Michael Key (as Laird's oddball assistant/martial-arts trainer) deliver hilarious supporting turns, and co-writer-director John Hamburg ("Meet the Parents," "Along Came Polly") delivers another solid dose of comic fun from a secular perspective. 

But be forewarned, that "Why Him?" definitely earns its R-rated status. Packed with crass yet clever raunchy humor, "Why Him?" is comic gold for most audiences, but if you're easily offended, it's not the movie for you.