"I might ask for a d**k double," Jackson responded, when Stern asked if he'd ever show his "ween."
"Do you feel your penis isn't big enough to show off on camera?" Stern asked, bluntly.
"I don't know if it's… yeah," Jackson confessed. "I don't know if it's formidable enough. My aura's so big, I don't know if my d**k is big enough to fill my aura."
Well, that also would explain why the 67-year-old actor has only done a few sex scenes -- including one with Juliette Binoche in In My Country and Naomi Watts in Mother and Child -- over the course of his career, noting "they're extremely awkward" to film as another reason.
"You ask before you start, 'Where can I touch you? Where shouldn't I touch you?'" he explained. "Then you apologize for both reasons. 'I'm sorry if I get excited' and 'I'm sorry if I don't.' Because sometimes it just ain't happening!"
Listen to the full interview below.
Unlike Jackson, Jason Segel is all about feeling "free."
Last month, the 35-year-old actor opened up to Variety about what it was like to go full-frontal for his role in Forgetting Sarah Marshall in 2008.
"The full-frontal nudity? I thought that was hilarious," Segel, who played Peter Bretter in the film, explained. "I was actually not very uncomfortable doing it. I really felt free. You have to put it in the context that this was 2006, 2007, and this hadn't been done before, in my recollection, where the main guy was going to be naked in the first five minutes of the movie."
In 2015, we saw a handful of celebs, like Khloe Kardashian, Justin Bieber and Selena Gomez, strip down. Watch the video below to hear more on the stars that left little to the imagination.