Seth Rogen's Engagement Story — Pops Question to Topless Girlfriend

Conan O'Brien's TBS debut marked the missed host's return to late night TV, and for the most part CoCo kept it clean. And then his first celebrity guest, Seth Rogen, managed to share a story about his fiancée's breasts.

The comedic actor candidly shared his engagement story to girlfriend Lauren Miller.

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"She was in our closet, changing, and she was literally only in her underpants," the Green Hornet star told Conan on his brand new show last night. "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."

"I figured the only appropriate thing was to place the ring on her nipple, actually," Seth, 28, quipped.

The redheaded host became a little nervous when Seth started throwing slang terms around for breast and using some expletives.

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"Hey, hey, hey, we don't have to throw it around!" the Conan yelled, before joking, "Thank God we're on TBS," after his first guest was bleeped a few times.

Breasts weren't the only topics on the table, Seth continued to discuss the controversial Proposition 19, sharing that he was in possession of a medical marijuana prescription.

"I've got a very specific ailment, it's called, 'I ain't got no weed on me right now,' " he quipped.

As far as the wedding planning goes, Seth said he finds himself more interested than expected.

"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.' "

Catch the interview below and be sure to tune into Conan, weekdays at 11 p.m. on TBS.