In “Bottoms,” a high-school comedy that is brazenly gonzo, scaldingly and at times even dementedly over-the-top, and actually about something, Pj (Rachel Sennott) and Josie (Ayo Edebiri) have been best friends since the first grade, but in their senior year at Rock Ridge High they’re at the end of their tether. They’re losers, they’re lonely, they’re lesbians — and in their eyes, that puts them beneath the bottom of the food chain. So they do what anyone in their position might do. They decide to start a fight club!

It’s modeled (sort of) on the one in “Fight Club,” though the movie isn’t particularly interested in that film, where the characters staged bare-knuckle brawls out of a kind of self-serious macho romantic doomsday nihilism. In “Bottoms,” Pj and Josie, in the time-honored tradition of teen-movie protagonists out to lose their virginity, are just looking for...