Bad Grandpa! Bad! (Paramount Pictures/ MTV Films) Bad Grandpa! Bad! (Paramount Pictures/ MTV Films)

In “Bad Grandpa,” out Friday, Johnny Knoxville, 42, plays Irving Zisman, who’s 86. The “Jackass” star can pull this off thanks to his outstanding acting ability … no wait, just kidding he just wears a ton of prosthetic makeup. He’s not the first actor to rely on rubber and plastic to get to the soul of his character.

John Merrick
In 1980’s “The Elephant Man,” John Hurt piled on everything but the kitchen sink to portray the heavily disfigured Merrick. Actually, there may have been an actual kitchen sink involved.

Frodo Baggins
In the “Lord of the Rings” trilogy, Elijah Wood’s Hobbit feet were big, hairy and fake, which is the standard uniform for any ring-delivery service.

In 2000’s “X-Men,” you had Hugh Jackman as Wolverine for those who like big, muscle-bound guys; then you had Rebecca Romijn for those who like naked, blue, scaly women. Something for everyone!

“Shallow Hal” taught us many lessons in 2001, notably that it’s always OK to laugh at a fat woman, but it’s only OK to love her when she’s actually Gwyneth Paltrow in a fat suit.

Dirk Diggler
You got to see the prosthetic that Mark Wahlberg wore in 1997’s “Boogie Nights” in only one scene, but it certainly had a huge impact. Um, left a big impression. Was massively important to the plot. You get what we’re talking about, right?