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The Big Bang Theory was in rare form this week and from the looks of things—it was a huge hit.

Penny and Leonard, played by Kaley Cuoco and Johnny Galecki, got all S&M with Penny dressed as a dominatrix.

Related: Kaley Cuoco in a bikini is a true delight

Social media caught wind of the fantasy get-up and it caused a frenzy.

But before you go thinking the show has gone all X-rated. The whole thing was part of a dream being had by Jim Parson’s character Sheldon.