Taylor Swift is a megastar, which gives her the power to surprise her fans with some of the most exciting guests on tour. While in London at the O2 on Feb. 4, the singer invited the Script onstage with her to perform the band's biggest hit, Breakeven.'

Swift was ever so coy before frontman Danny O'Donoghue joined her onstage. "You guys have such incredible music, such incredible artists and there's a band that I first saw when I came over here the first couple of times when I was 18," she started with excitement. "This was the first time I was exposed to this band before they blew up in America, too."

"They have incredible songwriting, unbelievable songs and they have a really great lead singer," Swift added. As the fans' screams began erupting in the building, Swift asked, "London, how would you feel if I were to tell you that Danny O'Donoghue ..."

That was all the crowd needed to hear; the songstress' last words were drowned out as the lead vocalist appeared.

O'Donoghue took the first verse of 'Breakeven,' letting Swift shine on the second. They harmonized, danced and had the arena full of fans on their feet, singing to the smash song. In the middle of the song, the 'Red' songstress turned sweetly to the crowd and said, "Oh, wow. Would you please say hello to my friend Danny?"

The former 'The Voice UK' judge certainly felt lots of love from the 50,000-plus London crowd.

With just three more dates left on her 2014 Red Tour overseas, it will be interesting to see if Swift brings any more surprise guests up on her stage. And by surprise guests, we don't mean uninvited surprise guests!