If, while watching this new Amy Schumer comedy, you get the feeling that you’ve seen something like it before, you won’t be alone. Once the premise got going, other films that came to mind included body-switching titles like “Freaky Friday” and “13 Going on 30.” This one even quoted from another film with a different but still-related plot device: “Big,” and the business of a young boy putting a coin in an arcade machine and saying, “I wish I were big,” then turning into Tom Hanks.

In “I Feel Pretty,” Schumer plays Renee, a New Yorker stuck in a dreary job and unhappy that she’s not slim and beautiful, that she has no luck with guys, and that she can’t see a way out of her rut. But she tries. She joins a cycle exercise class (that doesn’t go very well), she goes for a different look with an online hair tutorial (to no avail). She shops for clothing (but is told that items in her size “are limited”). She and her pals Viv and Jane (Aidy Bryant and Busy Philipps) try a dating service (but don’t get beyond the photo stage).

This is played for cheap laughs, and it feels a little cruel. Yet when Renee is alone at home, gazing in a mirror and feeling saddened by what she sees, there are no laughs. That’s a signal that Schumer is going to give a memorable performance here, and she doesn’t disappoint. She can make you guffaw and she can make you sigh.

In time, the film doesn’t disappoint, either. After a beginning that will make most viewers laugh while some will cringe, the script puts Renee on a path that will have most viewers rooting for her while some won’t approve of her behavior.

She’s a lowly worker who helps run the online site for a fancy, overpriced makeup line. One of her dreams is to make it to corporate headquarters where she can hang with the “beautiful people.” Her day is made when she catches a glimpse of the company’s CEO, Avery LeClaire (Michelle Williams, terrific in the part), who dresses too brightly, wears far too much really red lipstick, and talks the way Marilyn Monroe used to coo.

It’s after seeing Avery that Renee goes home, deflated by her own lot in life, and turns on the TV to see the kid in “Big” get the card that reads “Your wish is granted.” The unhappy woman runs outside, looks into a big fountain, tosses a coin and says, “I wish I was beautiful.”

Know this: “I Feel Pretty” has its plot moved forward due to someone getting knocked on the head, and not just once. When it happens, and when Renee awakes, and when she looks in the mirror this time and sees a “new, improved” Renee, the main story gets started.

But no one else sees her differently. Not in the movie and not in the audience. Renee has become delusional and is acting out her newfound beauty. Are we supposed to laugh at that? I didn’t, but a lot of people around me did. Yet a short while later, without noticing any specific change in mood or atmosphere or even in the style of humor, I found myself under the film’s spell.

Though some of the humor remains awkward and a little forced, it turns into a sweet but never cloying movie that takes time to get out a serious message: Be yourself. Then it gets funny again, sometimes via slapstick, sometimes under the guise of bathroom humor (taking place in a bathroom!).

Schumer does a romantic interest bit — with Rory Scovel as Ethan, a fellow she meets at a dry cleaner — as well as everything else she does in the film. The plot twist-heavy last act has things being funny, serious and briefly, a tad formulaic. But it all comes to the right kind of ending for this kind of movie, with that message of being yourself ringing loud and clear.

— Ed Symkus writes about movies for More Content Now. He can be reached at esymkus@rcn.com.

“I Feel Pretty”
Written and directed by Abby Kohn and Marc Silverstein
With Amy Schumer, Michelle Williams, Rory Scovel, Lauren Hutton
Rated PG-13