Lady Gaga -- It's No Illusion ... It's Her (VIDEO)

Lady Gaga can fill Madison Square Garden easy, which makes it all the more awesome she performed in an English pub that maybe fits 200 people.

Gaga made a surprise appearance at Moth Club outside London, and performed her new single, "Perfect Illusion" for the first time ever.

She showed lots of underboob and heart as the crowd went wild.

Who are we kidding ... this is clearly part of the marketing campaign. Still, awesome.