Billy Gardell and Melissa McCarthy star in “Mike & Molly”

Change is a good thing, or so they say. Now in its fourth season, “Mike and Molly” is starting to undergo some changes of its own.

Though it’s never proven to be explosively popular, in the ranks of sitcoms like “Seinfeld” or “Friends,” “Mike and Molly” has enjoyed steady viewership over the course of its run. The series revolves around a working-class Chicago couple who fell in love after meeting at an Overeaters Anonymous group. Mike Biggs (Billy Gardell, “Yes, Dear”) is a good-hearted police officer striving to lose weight and who tends to submit to his overbearing, cantankerous mother. Molly Flynn (Melissa McCarthy, “Bridesmaids,” 2011) is a good-humored fourth-grade teacher with a mound of debt from extravagant shopping habits and traveling. The couple married at the end of Season 2, and the series has explored their courtship and subsequent married life.

The show, now in its fourth season and airing Monday nights on CBS with a new episode premiering Feb. 3, is beginning to take on a new flavor in terms of content and storyline, particularly in the character and behavior of Molly. Previously rational, if quick-tempered, Molly is now going through a mid-life crisis that has led her to quit her teaching job (by way of jumping out of her classroom window) and take up a writing career. This scenario has served to place her in increasingly zany situations, from going on a ride-along with Mike as research for a crime novel to spying on her neighbor to driving a forklift in a warehouse.

The decision to morph Molly into a more physically comical character is primarily in response to McCarthy’s increasing popularity on the big screen. When “Bridesmaids” came to theaters in 2011, McCarthy acted alongside some of today’s top-drawer funny ladies in her role as Megan, the hilariously abrasive future sister-in-law of a bride-to-be portrayed by Maya Rudolph (“Saturday Night Live”). “GQ” called it “the bravest ... most balls-out, and hilarious performance of the year.” McCarthy received multiple nominations following “Bridesmaids,” including Best Actress in a Supporting Role. She also took home an MTV Movie Award for Best Comedic Performance.

McCarthy was hardly an unknown previous to “Bridesmaids,” but the movie truly made her a star – specifically a comic star, and one worthy of the silver screen. In 2013, she starred alongside Sandra Bullock (“The Blind Side,” 2009) in “The Heat,” and Jason Bateman (“Arrested Development”) in the admittedly poorly reviewed “Identity Thief,” both times in comic roles. Despite being mostly negatively received, “Identity Thief” opened No. 1 at the box office its first weekend: arguably drawing in fans due to the strong and well-known leads.

Melissa McCarthy stars in “Mike & Molly”

Her role in “Bridesmaids” was a strong departure for McCarthy from her sweet and sunny prime-time characters like Molly Flynn and Sookie St. James, the “Gilmore Girls” role with which she was previously associated. It’s therefore understandable why, following the actress’ big-screen success and popularity, producers would want to pull in the same McCarthy love for Molly that her film characters enjoy. It’s clear that they seek to accomplish this by having her act a little more crazily, incorporating in more physical comedy. “She and Billy Gardell have often been relegated to playing straight and reacting to the outsize characters around them,” Zap2it writer Rick Porter points out, “but here ... McCarthy gets the comedy spotlight and runs with it.”

Season 4 has been branded as “The New Mike and Molly” to account for these changes and in the hopes of making viewers – and potential viewers – see the series in a different light. So far, though, “Movie McCarthy” hasn’t done much to the ratings; they’re still not through the roof, but the new format hasn’t flopped, either. There is some skepticism that speaks to this apparent indifference, as Alan Sepinwall writes at Hitfix.com: “You can't just take Movie Star Melissa McCarthy and turn her into TV Star Melissa McCarthy. It doesn't automatically transfer from the big screen to the small, and it's not clear how much stardom matters at all on either these days.”

Indeed, there are numerous factors that play into how well a show is received, and it’s expecting a lot for one character’s portrayal to be responsible for bringing in hordes of previously disinterested viewers. With McCarthy getting the spotlight, there also lurks the potential for the character of Mike to be overpowered and even fall by the wayside. Like McCarthy, Gardell has a background in comedy and standup, though he hasn’t achieved the degree of fame his co-star has found in recent years. Then again, it's possible that acting the straight man to his now wacky wife will allow Mike to bring another level of comedy to the show.

Hit or miss, the decision to reboot an established series is always a bold move, and in the case of middle-of-the-road “Mike and Molly,” one worth trying. Tune in to CBS on Monday, Feb. 3. for the newest episode, and decide for yourself if the change is for the best.