Free throw distractions are hilarious. But pity the person at the line.

The idea took hold in 2013 at Arizona State. Why wave your arms to distract opponents at the free throw line, students wondered, when one of them could leap from a cardboard box at the right moment? From there it was a small jump to putting up a curtain, parting it at a crucial moment to reveal a Speedo-clad Michael Phelps and giving way to all sorts of outlandish efforts at distraction and intimidation.

This season, members of the Oakland University swimming and diving team, not content with foot-stomping, swaying, chanting and cardboard box-jumping, got into the act. A few weeks ago, video of the aquatic Golden Grizzlies gleefully shaving each others’ heads during free throws was shared nationally. From there, they took it to the team’s early Horizon League games played on their home court, rising to the postseason demand for more.

They waxed each other’s arms, legs and chests and gave Ian Allen an OU faux tattoo with a Sharpie.

There was a milk-guzzling contest during timeouts and halftime, too. “I was tatted up, waxed and full of milk,” swimmer Ian Allen proudly said of his commitment to a bit that grew after originating in the swimmers’ locker room, which they’d turned into a barber shop when most of them decided to shave their heads last month.

Allen, however, was reluctant and kept putting off the buzz cut — until swimmers decided they wanted matching hair “styles.” Allen agreed to shave his head before the basketball game against Horizon foe Cleveland State, and a teammate suggested he do it during the game. Armed with an electric razor and two trash bags, a viral moment was born as the shaving began amid team members, wearing swimsuits with “OUPRIDE!” spelled out in black body paint.

Jonas Cantrell, a junior who assisted with the razor, believes the head-shaving contributed to four missed free throws. “To take that team down to a [66.7] percent free throw average, it showed us we’re doing something,” Cantrell told The Post in February. Cleveland State had a 90 percent free throw average in its previous game.

“Nobody’s making more of a major impact today than the swimming and diving team,” announcer Tony Paul said.

Oakland went on to win the Horizon League tournament last week and earned an NCAA tournament berth for the first time since it went back-toback in 2010 and 2011. A 14th seed, the Rochester, Mich., school (23-11 overall, 15-5 in the Horizon) will play third-seeded Kentucky (23-9, 13-5 SEC) in a first-round game Thursday night in Pittsburgh.

The freewheeling fun pretty much ends as postseason competition intensifies, moving to neutral sites for conference tournament and NCAA games. At those venues, security is tighter, seating is at a premium and travel can be prohibitive.

Disruptions at Oakland and elsewhere are rooted in, among other examples, those created by Arizona State’s 942 student section and its “Curtain of Distraction” in the fall of 2013. When an empty