Liev Schreiber recalls the best erection of his life. And it wasn't with Naomi Watts.

Sometimes, celebrities say the darndest things.

Take Liev Schreiber, for example, who was just having a casual chat with Conan O’Brien when he decided to drop an ERECTION BOMBSHELL. (Is that a thing? If not, that definitely needs to be a thing).

Schreiber – who has been with Aussie goddess actress Naomi Watts since 2005 – was discussing his first ever movie role, in which he played a transvestite named Chris opposite Steve Martin.

The pair dance the foxtrot together in the film, but things got a little...err...hard during rehearsals.

"I thought to myself, 'Boy, would it be inappropriate if I, you know, became aroused'" he told Conan.

It seems the actor then learned about Murphy's Law the hard (sorry) way, when he got "probably the best [erection] I've ever had in my life".

"I'm mortified, because we haven't even shook hands yet...and every time he spins me, it's like 'thwack' into his leg!" he shared.

Yeah, that's SUPER awkward.

Thankfully, Steve kept the embarrassing secret from public knowledge...and then Liev went and told the story on an international talk show anyway.

Go figure.