Casting the perky, versatile Christina Bianco in the middling comedy “Application Pending” is like driving a Porsche around the block at 20 mph. What a waste of resources!

While theatergoers may recognize her from the “Forbidden Broadway” and “Newsical” revues, it’s Bianco’s YouTube videos — in which she morphs from Cher to Bernadette Peters to Celine Dion — that have turned her into a viral celebrity.

No wonder she seemed ideal for Greg Edwards and Andy Sandberg’s solo show, in which Bianco plays some 40 characters.

The main one is Christine, who’s just rocketed from kindergarten teaching assistant to head of “preprimary admissions” at a Manhattan academy.

Over the course of a day, mercifully condensed to an hour and a half of stage time, poor, harried Christine fields an unending stream of phone calls from rabid parents who try to bully, bribe and charm her into finding a spot for their precious toddlers.

“You may not be part of the 1 percent,” a girlfriend tells her, “but you control the fate of their children.”

Our rookie gatekeeper must also deal with other staff members, such as the director of financial affairs, a haughty Native American with a quick trigger finger when it comes to perceived racial slights. The playwrights (Sandberg also directed) lay on the satire of political correctness with a trowel.

As if this weren’t enough, Christine also battles PETA, discusses catering plans for the school banquet and somehow finds the time to flirt with a bashful single dad.

All of these exchanges happen over the phone, with Bianco deftly switching among characters — it’s amazing how she keeps track of them. But the conceit is not only repetitive, it strains credulity: Really, nobody ever drops by Christine’s office all day?

By the end of this frantic, yet hollow, show, public school has never looked so good.