Dwayne Johnson 'Hustles for the Muscle' With Jimmy Fallon (Video)

The pair played the beefed up "Fungo Brothers" in a series of spoof workout videos, while David Letterman grilled Ricky Gervais about his love life on the "Late Show."

Workout videos are big business  — and so is Dwayne Johnson.

The Hercules star revealed his secret to getting beefed up in a collection of fake fitness videos with Jimmy Fallon on The Tonight Show on Tuesday.

Among the unique workouts were the squat thrust twist during which they reminded viewers that "you have to hustle for the muscle," followed by their own version of the Shake Weight.

The host also accused Johnson of "breaking the Internet" after he posted an old photo from his younger, less cool years. "Any time you have a leather fanny pack, you must insert the thumb," joked "The Rock" about the flashback.

Fallon later showcased the "new Hercules action figure, coincidentally wearing the same turtleneck sweater, leather fanny pack and with a tissue under his arm," just like the old picture. 

PHOTOS Exclusive Portraits of 'Hercules' Star Dwayne 'The Rock' Johnson

Mother of two Kate Hudson told Seth Meyers she was "all taped in" to her tight dress on Late Night, before revealing that she has to censor the films that her 10-year-old son watches. "Ryder has seen all the ones [she stars in] that he can see, but he is more interested in the ones he can't see," because he always asks if she's naked in them.

Over on CBS, David Letterman quizzed Ricky Gervais about his love life, asking: "Did you ever marry that woman?"

The blunt question sent the British comedian into bursts into laughter, forcing him to admit, "We are not married, but we have been together for 30 years," said Gervais, adding that there is no point in getting married because "we have enough toasters and don't want our families to meet."