Mitch and Dave have been best friends since boyhood. In The Change-Up, they maintain that friendship even though their lives have taken vastly divergent paths.

Mitch, a none-too-successful actor and high-school dropout, is one those guys whose social and civic development stopped at 13. Dave, on the other hand, is a professional, a hardworking lawyer with a major firm. He has much responsibility at home, too, including a young daughter and newborn twins.

Recalling the saying about the grass being greener on the other side, Dave turns to Mitch during a sports-bar man date and laments, “I missed all the sex and bad choices.”

Later, as the alcohol-saturated guys simultaneously urinate into a public fountain, each of them turns to other and says, “I wish I had your life!”

That said, lightning strikes. The full effect of Mitch and Dave’s magical mystical transformation, however, won’t hit them till they awaken the morning after. It will be an especially stressful day. As has happened multiple times in movies through the decades, the guys are transferred into each other’s body.

All Of Me, a 1984 comedy starring Steve Martin and Lily Tomlin, is among the better body-switching movies. The Change-Up is among the worst. Another of Hollywood’s gross-out comedies, it stars Ryan Reynolds as the incorrigibly selfish and irresponsible Mitch and Jason Bateman as the sober and serious dad and husband Dave.

The switch having been made, Mitch and Dave must pretend to be each other until they can reverse the mysterious spell. Of course, they each botch the role-playing duties that have been forced upon them. In true romantic-comedy-meets-gross-out-comedy style, they also learn life lessons and engage in the forced, clichéd moments of sweetness that supposedly mitigate the gushing crudeness that pollutes movies of this ilk.

The Change-Up is especially thick with crudeness.

There are bathroom jokes, baby-poop slapstick, frequent F words, sex during advanced stages of pregnancy and, for conservative Dave in the guise of the hedonistic Mitch, a disturbing visit to a porno movie set.

Hypocritically, everything works out happily in the end. Lessons are learned and, lives, in ways other than body switching, are transformed.

In reality, things aren’t working out so well for The Change-Up. Widely thumped by critics, it’s also stumbling at the box office.