Three’s a crowd: Joy with Ron (right), a tiger and their lover

THERE'S a good Chris Rock gag about the hysteria surrounding the circus tiger that mistook Roy Horn of Siegfried & Roy for a snack. It goes like this:

“That tiger didn’t go crazy; that tiger went tiger! You know when he was really crazy? When he was riding around on a unicycle with a Hitler helmet on!”

Well, exactly. And if you know the line, it’s pretty much the only thing you’ll be able to think of while watching tonight’s utterly engrossing but equally maddening doc Cat Dancers. It too features a glitzy showbiz act involving animals. It too ­features performers convinced their lovable 130lb jungle killers adore them. And it too ends rather horrifically, with necks being playfully punctured and blood spurting out before they have time to say “but… Twinkles… why?”

In short: tigers go tiger.

This story is about dance duo Joy and Ron Holiday, an “exotic tiger entertainment” act, who started out in ballet but ended up spinning Bengal tigers on wheels, catching flying leopards, and doing the tango with a

direct descendent of a sabre-toothed tiger.

As you watch the footage, the question you ask yourself isn’t so much “My God, how did it happen?” as “My God, why aren’t those tigers eating them right now? What on Earth took them so long?”

No prizes for guessing who eventually cops it as the entire documentary is told from Ron’s perspective, talking us through everything from his early animal-raising days (“New York City,” he ­informs us, “was no place to raise a black leopard”) to some frankly rather disturbing shots of him posing with a panther in his pants (him in his pants, you understand, not the panther).

Get past Ron’s inherent ridiculousness – he’s ­forever sporting wigs I’m shocked the tigers don’t try to attack – and the tale is a tragic one, an instance of projecting ­ourselves on to animals, with the twist of a newcomer who ­became both Ron and Joy’s lover.

Yet one thing is never ­mentioned: children. It’s clear the cats became the kids they never had. And just as boys will be boys, tigers will be tigers.