Rogen, 28, had grand plans for the proposal but claims he had to improvise when he raced into the room to pop the question only to realize his actress girlfriend was topless.
"She was in our closet, changing, and she was literally only in her underpants," Rogen told Conan O'Brien on his brand new TBS talk show Monday. "I had already kind of started [to propose]. … I didn't picture it like this, and I know she didn't picture it like this."
So, how did he handle it? "I figured the only appropriate thing was to place the ring on her nipple, actually," Rogen joked.
The actor also talked about the wedding planning, and the curious feeling of actually having an interest in the details.
"I find myself having opinions about what our centerpieces should look like," he said. "And I'm like, 'What am I doing? I don't care about any of this stuff at all.' "