This is amazing.
It was one of Calvin Harris' biggest DJ sets of the year, so you might expect him to drop a surprise or two - but no one at T In The Park expected the Scottish DJ to bring out Will Smith last night (12th July).
The rapper-turned-actor introduced Calvin on stage, telling the festival crowd that he had been told that he had to come to the festival because he was "looking for an experience".
"Ladies and gentleman, I present to you - Scotland's own, Calvin Harris," the Fresh Prince said.
He later joined Calvin Harris again during 'Summer'. You can watch it above.