BOTTOM LINE: It’s like watching two guys with multiple personality disorder on uppers.

Know who the two hardest-working men in show business are? They have to be Robert Stanton and Daniel Jenkins, the sole cast members — and playwrights — of off-Broadway’s Love Child, who tackle 22 characters between them. Their 90-minute, intermission-less play-within-a-play is an energetic marathon of characters, voices, and sound effects, and Stanton and Jenkins do it all. These two guys manage to tell a very full story with — well, with just themselves. And it’s pretty hard to believe even as you’re watching it.

Love Child is a love letter to the theatre. The story centers on Joel, a performer, writer, and director currently starring in his own off-off-Broadway play, which is not so coincidentally called Love Child. It could be his big break since there are some producers in the audience, but in true farcical fashion, everything that could go wrong does. Out of the madness stem overdramatic reactions as the cast and crew try to cope. Subsequent hilarity ensues.

Plotwise, Love Child isn’t exceptionally unique or exciting. Theatre about theatre frequently feels stale, and it’s hard to avoid navel-gazing when the line between onstage and offstage is so thin. Maybe I’m just jaded because it’s such an overused theme, but you don’t go to a play like Love Child because you want Shakespeare. Frankly, the plot is just a vehicle for Stanton and Jenkins to deliver hilarious characterizations and show off their tremendous comic chops.

I can’t really describe the speed at which the two actors flip from one character to another, but most of the time there are more than two characters onstage. With clever nuances like posture, gestures, vocal inflection, and pitch, all 22 characters are specific, and it’s usually simple to distinguish one from another.

That doesn’t mean the story is easy to follow, though. It’s a freakin’ whirlwind, after all. But in terms of clarification, Stanton, Jenkins, and director Carl Forsman do a noble job keeping Love Child on track. The staging helps, as Forsman establishes placement for each character, and to keep things interesting, Stanton and Jenkins use the whole space to their advantage, sometimes even jumping into the audience when appropriate (the story does take place in a theater).

It’s obvious that Stanton and Jenkins are first-rate performers; their hefty bios include dramas, classics, and musicals as well as comedies, which pretty much leads me to believe there isn’t anything these two can’t do. But aside from my awe for the performances Love Child offers, the show offers a fun night at the theatre, too. You have to pay attention, so I can’t say it’s total escapism, but it isn’t heavy stuff, either. It’s simply an entertaining 90-minute ride.

Love Child plays a limited engagement through January 3 at New World Stages, 340 W. 50th St., between 8th and 9th avenues. Performances are Mon and Wed-Fri 8 PM, Sat 4 and 8 PM, and Sun 3 and 7 PM. Tickets are $69.50-$99.50, but you can use discount code LCBBOX909 for $29.50-$39.50 tickets; to purchase, call 800-432-7250 or visit telecharge.com. For more show info, visit lovechildtheplay.com.