In the fourth episode of the HBO series's most recent season, Manganiello's character Alcide comes face-to-face with Eric as he swims in a lake. In the scene in question, the two fight over Sookie (Anna Paquin) entirely in the nude as she looks on.
Manganiello recalled the infamous scene, revealing that it was shot on Valentine's Day.
"It was Valentine's Day, and there's me and Skarsgård naked, screaming that were going to kill each other, with Anna in the middle and my wolf Thunder a few feet away," he told TV Line. "There were a lot of 'Happy Valentine's Day, Anna' jokes going around."
Manganiello recently revealed that he is comfortable with being naked on screen, considering nudity to be "just a typical day at the office".
The actor was rumoured to have split from his fiancée Audra Marie earlier this week.
True Blood concluded its fourth season last Sunday.
Watch Alcide and Eric's naked confrontation from True Blood below: