Mae Whitman sasses, sashays and sparkles in "The DUFF," a snappy, sweet-spirited teen comedy about a smart girl who tries to fight high school labeling with wit and words. And the occasional punch.

It’s a paint-by-numbers romantic comedy. But Whitman, best known for TV’s "Arrested Development" and "Parenthood," clicks with her co-stars and handles the screenplay’s zingers and the droll voice-over narration her character spouts in this feature from director Ari "West Bank Story" Sandel. Sandel keeps everybody talking so fast they talk over everybody else, and as we know, in comedy, quicker is always funnier.

Bianca (Whitman) is the plain-Jane honor student and school newspaper columnist whose shrewd observations about the hierarchy at Mallow High School don’t include self-observation. She’s pals with two of the hottest girls in school (Bianca A. Santos, Skyler Samuels), but only her amusingly tactless hunk-jock neighbor, Wesley (Robbie Amell), will tell her the truth.

She dresses dumpy, carries more weight than some, and therefore, she’s the "DUFF — Designated Ugly and Fat Friend" to her two hot friends. She is invisible to her peers, merely the approachable gateway to the sexy and the gorgeous.

Being a clever girl, she resolves to swap coaching Wesley in chemistry in exchange for his makeover coaching. Can he turn her from "the approachable one to the datable one" in five or eight easy steps?

You know the answer.

Bella Thorne is typecast as the bombshell mean girl, and it’s a credit to this script that her character is the only cardboard one in "DUFF." Wesley is cocky and distracted but not stupid, and he gives as good as he gets with the insulting smart girl he’s teaching to fit in. How’s she doing at the whole approach-a-boy-and-flirt-with-him thing?

"You’re horrible. I hope you like cats."

Amell is unusually good at the film’s rushed one-liners.

Social media shunning and a nasty/funny viral video point a spotlight on bullying, which freaks out the bullying-expert principal (Romany Malco).

"Have you not seen ‘Dateline,’ ‘Catfish,’ ‘Pretty Little Liars’?"

Ken Jeong brings a sympathetic sarcasm to his journalism teacher character, and Allison Janney, as Bianca’s dumped single mom turned motivational speaker, tears through slogans like Tony Robbins on speed.

"Believe. Retrieve. Achieve. Just don’t conceive!"

It’s a little vulgar, like real teens, and only in Hollywood would a glamour puss like Whitman, ears bedazzled with piercings, uninhibited and fun, be anyone’s idea of a frumpy DUFF. But the sexuality is toned down and the messages so girl-friendly that formulaic or not, this "DUFF" is a winner and Whitman, in what will probably be her last teen role, proves that she’s still a starlet worth watching.

Review by Roger Moore, Tribune News Service