The two stars sat down with ET recently, where they opened up about the bizarre, brazen comedy that has regularly divided audiences with its grotesque humor and unusual plot.
"I think we knew what we signed up for," Radcliffe, 26, shared.
"Yeah, we were all in it together," Dano, 32, added.
The film follows Hank (Dano), a man marooned on an island who comes across a fresh corpse (Radcliffe) that has washed up on the beach. Hank makes friends with the dead body, whom he names Manny, and strikes up a very surreal friendship with the deceased as he pulls the corpse along with him all over the island.
"Dude was just getting dragged around and never complained once," Dano said, praising Radcliffe's commitment to the role.
Hank soon discovers that Manny has many useful survival applications -- like a Swiss Army knife, hence the title. One of the most talked about ways Hank uses Manny's body is as a makeshift boat, propelled by the corpse's decomposition-related flatulence.
And it turns out this isn't even the strangest thing Dano and Radcliffe had to do together in the film. For example, there's one scene in which Hank kisses Manny's dead lips. However, as Radcliffe pointed out, "the kissing thing is not even the remotely the most intimate thing we do in the film."
After all, there's also a scene where Hank sticks his hand in Manny's mouth to grab his tongue and wiggle it around. Dano recalled the sensation of grabbing someone's tongue, sharing, "For some reason it's very weird."
Despite the unorthodox premise, Radcliffe is confident that his dedicated legion of "Harry Potter" fans will end up digging the crazy comedy.
"I think that, generally speaking, 'Potter' fans are curious and open, and I think most of them will enjoy this movie," Radcliffe said.
And for those who aren't even willing to give the movie a try, Dano has a very simple message: "Your loss."
"Swiss Army Man" hits theaters on Friday.