Snakes, shaves, dodgeballs: Robert De Niro endures his greatest film blows in 'War With Grandpa'

Not since "Raging Bull" has Robert De Niro taken the kind of on-screen blows seen in "The War With Grandpa."

De Niro's Grandpa Ed undergoes multiple traumas and emotional distress facing off against his 11-year-old grandson Peter (Oakes Fegley) in the battle over a bedroom in the unapologetically silly comedy (now in theaters).

"He takes it everywhere, on the chin and the chest. He's definitely a punching bag for a little kid," says director Tim Hill, who says De Niro, a two-time Oscar-winning legend, encouraged adding more gags and never complained.

Before showing up on set, De Niro, 77, even wrote a handwritten greeting note to Fegley.

"That was so nice, and took away some of my nervousness," says Fegley, who adds, "I never warned him of the trauma coming his way."

Let's break it down:

He dodged balls on a Sky Zone trampoline

De Niro donned those orange nonslip socks to hit the Sky Zone trampolines with co-stars Christopher Walken, Cheech Marin and Jane Seymour, battling Fegley and his younger cohorts in dodgeball. Parents don't need to be told the rigors of even walking on these trampolines, much less jumping for days for cameras. The dodgeball attacks didn't stop, either. "In between takes, like, a kid would take a shot at him," Hill says.

Fegley admits that De Niro could hurl right back. And Ed does get serious air for a show-stopping throw, with help. Hill says they used a harness and wires in the scene.

He went unhinged through a door, lost his marbles

Peter removes the hinges from the contested room's door, so that when Ed leans on it, he flies through the frame onto the ground with the door. Ed also drops a keepsake marble collection jar, boobytrapped by Peter, and slips wildly onto the floor among the marbles.

De Niro shot as much as vigilant filmmakers allowed around the scenes. Stunt professionals took the impact moments of each fall.

"Bob was willing," Hill says of the door fall. "But I told him, 'Eh, I want you to come back tomorrow.'"

He shaved with foam sealant, dropped his towel

The art crew constructed a special foamlike chin mask for De Niro to shoot a scene where Peter replaces Ed's shaving cream with fast-setting foam sealant. De Niro had no problem shooting the scene with Ed in a towel, which ends up falling in front of mortified son-in-law Arthur (Rob Riggle).

"Bob's not shy or modest," says Hill. "It was in the script, and he just did it." De Niro was wearing movie set undergarments, but Riggle showed off a wide range of award-worthy scream reactions at the sight.

"This will never be spoken of," Ed says.

He spooned with a giant snake, fell off a roof

As the intergenerational battle escalates, Peter places a large snake in Ed's bed. De Niro had to shoot multiple takes with a significantly sized gopher snake.

"They're not poisonous, but they get really big and look really deadly," Hill says. "Bob was like, 'Snake? No problem.'"

De Niro had to stop a few takes as the snake was moving under the covers and missing its mark.

"Sometimes snakes don't stay where they are supposed to stay, especially under a blanket," Hill says.

Ed is so freaked out by the snake, he flies out the window, falls down the roof and hangs from the gutter in front of a window. Arthur watches in horror from the window as Ed's pajama bottoms continue the journey downward, giving another eyeful.

Hill says De Niro shot some gutter scenes, splitting duties with a stuntman.

"He was hanging from the gutter. We had something for him to stand on. But he wanted the shot to look good," Hill says. "At the end of the take, Bob did a pull-up on the gutter. He's fit."

He took ketchup fire in a condiment battle, returned mustard fire

Peter, armed with a ketchup bottle, faces off in a final fray against Ed, who shoots back mustard. Condiment war is hell.

"Every time we did it, the wardrobe people would have to clean us off, and we did it again and again," Fegley says. "I changed clothes, like, four times in that scene alone."

On-screen, it's an eye-opening draw. But Fegley admits De Niro won that battle with pure mustard soiling power.

"My pants were stained for the rest of the shoot," Fegley says.

This article originally appeared on USA TODAY: 'War With Grandpa': How Robert De Niro endures his greatest film blows