Regular readers are surely tired by now of my raving about what a genius Will Ferrell is, but “Bewitched” adds another chapter to my thesis. Here is a badly paced, poorly constructed movie that is equal parts goopy romantic-comedy and toothless Hollywood satire — and yet Ferrell makes it not just watchable, but even recommendable. And without him, it would be unbearable.

Ferrell plays Jack Wyatt, a fatuous and phony Tinseltown star whose career has taken a nose-dive since the recent highbrow bomb “Last Year in Katmandu.” (“The only DVD to sell NO copies,” observes his agent Ritchie, weaselishly played by Jason Schwartzman). He has been reduced to the ultimate indignity of taking a lead in a TV sitcom, a remake of “Bewitched.” But with Ritchie’s encouragement, he demands that the writers make the show more about Darrin (i.e., Jack Wyatt) than about Samantha. All he needs is some no-name to play Samantha, an actress who won’t notice that she has few lines and who will be a good straight man for Jack’s half-hearted slapstick.

Enter Isabel Bigelow (Nicole Kidman), a witch who has just popped up in L.A. to make a normal, non-magical life for herself, to the chagrin of her swingin’ warlock father (Michael Caine). While browsing at a bookstore, Jack sees her absent-mindedly twitch her nose, and she is cast as Samantha based on that skill alone. She’s reluctant at first — her people always hated the misrepresentations perpetrated by “Bewitched”; besides, she’s not even an actress — but she relents when Jack says he needs her. See, Isabel wants a man who needs her, a man who is a mess who she can straighten up with the everyday-housewife skills she is just learning. Jack, with his often-unshaven face and his clearly immature attitude, is just the fixer-upper she wants.

So an actual witch has been cast as Samantha; hilarity should ensue. The problem is, the screenplay has been written by chick-flick veterans Delia and Nora Ephron (and directed by Nora), and they show no prowess at all for a self-referential TV update-turned-spoof. Isabel is given almost as little to do as Jack’s version of Samantha is, and the episodic movie can’t figure out what to do with Kidman’s talents (let alone those of Isabel’s friends, played by Kristin Chenoweth and Heather Burns). In one extended sequence, Isabel goes on a date with Jack and nearly falls in love with him — but then, regretting it, reverses time, undoes the date, and starts over. Beware of a movie that tries to tell you an entire 10-minute segment never happened.

Isabel must eventually tell Jack her true nature, of course, and there the movie is comfortably in rom-com territory (revelation of truth; tearful breakup; montage of both parties missing each other; reconciliation). But in the meantime, you have Will Ferrell to enjoy. He is spot-on in his parody of a self-centered Hollywood jerk (“Make 20 cappuccinos and bring me the best one,” he tells his staff upon entering the studio one morning), and even funnier during the part of the film where Isabel has put a hex on him to make him appreciate her, a hex that goes too far and makes him a fawning idiot. From egocentric jerk to lovestruck dork, it’s all in a day’s work for Ferrell.

The Ephrons were wise to let Ferrell work up some of his own dialogue (his old “SNL” collaborator Adam McKay was reportedly called in to help, too); casting Ferrell’s pal Steve Carell as Uncle Arthur was smart, too. He does a hilarious Paul Lynde impression, making his few minutes in the film one of the highlights.

In all, it’s a rather charming and delightful comedy, its many flaws notwithstanding. A straightforward big-screen adaptation of the old show would have been superfluous, and if the concept they came up with doesn’t entirely work, at least it doesn’t fall flat. And we Ferrell fans have another respectable work to add to the canon.

B- (1 hr., 45 min.; PG-13, some scattered vulgarity, a little very mild profanity, very mild innuendo -- a PG movie that's been mis-rated.)