The girl near the gate flashes a Ziploc baggie filled with powder. “Hey!” she says. “Want some glitter?”

It’s Monday night at Wolf Trap and thousands of teens are pouring in to see Ke$ha, the 26-year-old pop star who encourages her fans to dust themselves in craft-store supplies and feel great about being alive.

It’s one of the most surprising bookings at Wolf Trap in years, but then again, maybe not. Ke$ha’s most intoxicating song, “We R Who We R,” promises “we’ll be forever young,” and the loyalty of her flock makes it easy to imagine them gathering at this tradition-friendly venue in the summer of 2043.

As the sun sets on Wolf Trap, the mood is skittish and polite. Smiley girls snap smiley selfies with smiley cops. Men wear cerulean lipstick that signals frostbite or a blue Icee habit. Near the concessions, a teenager in a “MOM IT’S MY LIFE” T-shirt walks silently alongside her mom, past a spill of gold glitter into which another teenager belly-flops. She does the worm, laughs, stands up, inspects her sparkliness, then laughs some more.

Everyone is dressed for one of the best evenings of make-believe in pop music — one where kids can pantomime rebellion in a safe space. Nobody here is actually going to do the things Ke$ha sings about. Like an amusement park roller coaster, what’s about to happen will provide the illusion of danger at very high volumes, and with lots of screaming.

Ke$ha strides onto the stage, looking like she fished her leotard out of a comic book, kicking her legs, grabbing herself, yapping about sex, liquor and the intersection of the two. But when she declares, “We are the crazy people,” during the refrain of her latest single, “Crazy Kids,” it feels a bit desperate.

That’s because this summer, everything Ke$ha has ever brought to the table of American pop music seems to have been repossessed. Nasal raps are the dominion of Nicki Minaj. Affirmation anthems will be sung by Katy Perry and Lady Gaga. The uncomfortable appropriation of hip-hop by inelegant white girls is being handled by Miley Cyrus.

But Ke$ha stays the course. She raps about Diddy. She name drops Iggy Pop. Her dancers thrust around in eyeball helmets similar to those worn by outsider rock troupe the Residents. The rest of the time, she’s She-Ra fronting Jem’s Holograms for thousands of shrieky kiddos who weren’t even alive when those cartoon characters inspired ’80s babies to write songs and ride unicorns.

It isn’t really working. “Blow” has an illicit thunder appropriate for strip clubs, soccer arenas, Michael Bay movies and Wolf Trap. Yet, somehow, Ke$ha’s presentation manages to feel as contrived and hammy as a bad Broadway routine. Her lyrics celebrate the reckless indulgence of impulses, but this show has been choreographed too tightly, all the way down to the fake-spontaneous crotch grabs. Spewing beer and flipping birds, Ke$ha hits all of her marks.

The performance approaches its finale with her irrepressible 2009 debut single, “Tik Tok,” and all Halloween breaks loose. Ke$ha is flanked by a giant inflatable pig and four dancers — one dressed as a tiger, one dressed as a chicken, two in drag. They’re the crazy people, remember? But shhhhh, they’re just pretending to be, and only for the next 15 minutes.

When the house lights finally go up, the songs have tucked themselves into your hippocampus, even if you didn’t like them, and the glitter has migrated onto your person, even if you didn’t do the worm. There’s an orderly march out of the gates, across the grassy parking lot, past the idling party bus, toward a queue of cars filled with moms and dads gazing into their phones, faces illuminated by “where r u?” texts.

Their children will suffer no hangovers on Tuesday morning — just cheeks sore from smiling and a ringing in the ears as persistent as the motorized sucking of gas station vacuum cleaners inhaling metallic flecks from so many Honda Accords.