I'm not sure I've heard the word "new" thrown around as often in a marketing campaign for a show entering its fourth year as I have for "Mike & Molly" — or, as all the CBS promos have dubbed it, "The New Mike & Molly" — which returns tonight at 9. Though the ads don't entirely hide the fact that this is a show that has existed for several years, we're told over and over about all that's new about the new "Mike & Molly," as if emphasizing that thought enough might subconsciously convince the audience that this is a first-time debut.

Why would CBS do this? Conventional wisdom in the TV business is that it's much easier to get viewers to sample a new show than one that's been around before — especially if it's a show they tried once and didn't like enough to watch a second time. "Mike & Molly" has been a modest success but never a big hit. The idea, it appears, is to convince the audience that Movie Star Melissa McCarthy has a brand-spanking new sitcom that they really ought to try, given how much they loved her in "Bridesmaids" and "The Heat" (and how much money they spent to see her in "Identity Thief"). And if a bigger audience is suckered in this way, they'll find a revamped version of the show with both an obvious entry point and a blatant attempt to make Molly seem more like McCarthy's film characters. Once-devoted school teacher Molly abruptly decides to quit the job she now hates (in mid-class), falls out of windows, gets into fights in bars and otherwise makes Mike fear for her sanity. (To make connections to "The Heat" extra-strong, we even see Molly go on a police ridealong with Mike where she gets mixed up in his attempt to see to a domestic disturbance.)

But even if CBS could Eternal Sunshine the entire population into forgetting the existence of the previous three seasons of "Mike & Molly," I'm not sure how much good it would do. 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.

There's a saying hit TV shows make stars, and not the other way around, and there's ample proof of that. Almost no one knew Bruce Willis before "Moonlighting," George Clooney before "ER," or the Friends before "Friends." And those people had higher profiles before those shows than Jim Parsons did pre-"Big Bang Theory."

Big names can bring in an audience sometimes for a new show's launch, but it has to be the right star with the right show, and maybe not even then. More often than not, these stars are actually years (if not decades) removed from their commercial peak, and in some cases only vaguely qualified as stars in the first place. NBC has to be enormously disappointed in the ratings for "The Michael J. Fox Show," and while Robin Williams' "The Crazy Ones" has done acceptably for CBS, its numbers are artificially inflated by airing on the same night as "Big Bang." And that's before we even talk about shows built around actors like Christian Slater, James Woods or Geena Davis, who had name value but were at a point in their careers when no one would cast them as the lead in a movie, and whose TV vehicles crashed quickly. (Slater alone has killed shows on NBC, ABC and FOX, meaning it's CBS' turn eventually.) Even Dustin Hoffman — multiple Oscar-winning, iconic movie legend Dustin Hoffman — couldn't get more than the tiniest of audiences to watch his HBO drama "Luck" during its brief life.

Even honest-to-goodness TV stars (and Fox has attained stardom in both places at different points) don't have much of a leg up on unknowns. Actors who've been the leads in multiple hit series are the exception, rather than the rule — which is why all that mid-'00s talk of a "'Seinfeld' curse" was idiotic. Familiarity with the star might be a thing that a viewer would consider when picking a new show, but it's rarely the primary thing.

For the most part, the audience falls for characters or concepts they want to follow every week. The actors sure help a lot — in the hands of a lesser performer than Parsons, Sheldon would be unbearable — but the love for them in a particular movie or TV role doesn't automatically translate to other shows. "Friends" fans adored Matthew Perry as Chandler Bing, but they didn't want to watch him as a depressed comedy writer on "Studio 60," a depressed sports arena manager on "Mr. Sunshine (Yay)" or a depressed widower on "Go On." Even bringing multiple actors from a beloved show back together doesn't accomplish much: when Jennifer Aniston stopped by Courteney Cox's "Cougar Town," the ratings needle barely moved.

Though the barrier to entry from TV to movie acting was shattered decades ago — Bryan Cranston seems to be in every other movie released these days — stardom on television also doesn't automatically lead to success in the movie business. Parsons, whether by his own choice or lack of opportunity, hasn't done much of note during his "Big Bang" hiatuses, making him even more typecast as Sheldon. (Fox had the good luck to have "Back to the Future" come out while he was still on "Family Ties," which kept him from being too closely identified with any one role.) Last week, Hollywood Reporter ran a story wondering why the stars of "The Walking Dead" haven't gotten lots of movie offers; in that case, it seems less that audiences only want to see these actors in these roles than perhaps an industry belief that the true stars of "Walking Dead" are the zombies, and you can't put their names above a movie title on a poster.

Besides, the movie business is beginning to question how many actors should still be considered genuine, bankable stars, whom the audience will pay to see no matter what the film is. (Even Will Smith had a flop this summer with "After Earth.") And there may be some debate about whether McCarthy deserves the star title at this point: she was a supporting player in "Bridesmaids" (albeit the one who got most of the laughs and the Oscar nomination) and for "The Heat" teamed with an unquestionable star in Sandra Bullock (though, again, she drove the comedy while Bullock played straight woman). On the other hand, the genuinely terrible "Identity Thief" made about as much money as the other two, and as much as I like Jason Bateman, I don't think many people were buying tickets specifically to see him in that.

"Mike & Molly" actually debuted the fall before "Bridesmaids" came out, or else CBS might have been able to do a much more elaborate marketing blitz for the premiere, rather than simply pitching it as another Chuck Lorre-produced sitcom. But prior to this season, Molly hasn't been nearly as crazy a character as McCarthy has played in her big hit movies, at least not on a regular basis. (She won an Emmy after the first season — and right after the "Bridesmaids" success — perhaps because Emmy voters are more impressed with movie stardom than average viewers, or perhaps because she got to play amusingly drunk in her submission episode.) It's been a small, sweet, old-fashioned kind of show. Even an audience ushered straight from the multiplex to an episode of "Mike & Molly" wouldn't feel like they were having the same kind of comic experience they got at the theater.

So it's easy to understand why "Mike & Molly" might be trying to reverse-engineer itself into something more closely resembling McCarthy's movies. And if that magically turned the show from a solid performer into a hit, I'd be happy for McCarthy. I loved her as Sookie on "Gilmore Girls" and have laughed up a storm watching her in both big movie roles and smaller ones (her obscene, improvised outtake from "This Is 40" is amazing). But making a hit TV show is generally more alchemy than science: the right combination of actor and character, of premise and execution, and often of outside circumstance. (If you swapped the networks and timeslots for "The Michael J. Fox Show" and "The Crazy Ones," I suspect their ratings would swap as well.) CBS can try and try to gets its viewers to notice that they've got a genuine box office sensation headlining a show on their network, but the audience has to want to see McCarthy in this specific role, on this specific show, done the way they want it.

Alan Sepinwall may be reached at sepinwall@hitfix.com