Gaga was almost unrecognisable underneath a mask-like hat and giant silver disc worn to collect the Best Female award at the Belfast ceremony.
She joked: “I’m really smiling right now — I know you can’t tell. I’ve had a lot of Botox.”
She also made a gag about David Hasselhoff’s manhood as he presented her with the award.
Replying to an earlier joke by the Baywatch star – who claimed to have drilled a hole in his dressing room wall – she praised his “big p**is.”
The Hoff joked: “All the nominees are very beautiful women. In fact there are a lot of beautiful women backstage in the dressing room next to me.
“In fact, I drilled a hole in the wall – in case they want to watch me changing.”
She wore the red costume to sing new song Marry The Night on top of a huge cratered moon.
