The presenter was larking around at the side of the stage during the ITV show's auditions, as one hopeful attempted to beat the world record for breaking coconuts with his hands.
Deciding to give it a go, Ant ended up cutting himself when he headbutted one.
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The moment was revealed in a new video from behind the scenes, which was shared on Instagram.
In the clip, the TV star first tried crack the fruit with his fist but howled when he made contact with it.
“Do not punch coconuts kids, it really hurts!” he exclaimed.
“I think I nearly broke my knuckle,” Ant said, as co-host Dec Donnelly warned viewers not to try it at home.
Both then took turns rapping it, before Ant tried to smash it with his forehead.
He didn’t seem to notice he’d hurt himself until Dec pointed out that he was bleeding.
“He’s cut his head on a coconut,” he said, as they called for help.
“How coco-nutty is that?” he quipped.
A medic then told Ant he was going to need a bandage, which surprised him.
“This is very extreme for a little tap on the forehead!” he said.
But Dec told him: “You are going to have to. You have to stop the infection.”
The medic and Dec couldn’t resist teasing Ant about how long he’d need the dressing, joking that it would be three weeks.
“That’s a nasty cut that is,” Dec said.
Undeterred by his wound, Ant returned to the stage after being treated to try again with the fruit.
Punching a few coconuts, he moaned: “It really hurts.”
Dec couldn’t stop laughing as he tried to get his co-star to give up.
“It’s not worth it, it’s not worth it!” he giggled.
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