Taylor Swift and Haim's friendship just reached new heights...thanks to Nelly.

To celebrate the sisters' last night on the 1989 World Tour, Taylor invited them up on stage to join her as a back-up dancer and singer for Nelly, who wowed his hometown crowd of St. Louis with his hit "Hot in Herre."

The performance was literally everything as Haim came out on stage just like Charlie's Angels.

As Nelly rapped, Taylor and the three sisters showed off their dance moves they made up the day before in their dressing room.

And, of course, they nailed all their backup vocals.

It's no surprise that Nelly killed his two performances with Taylor that night (they also sang his song "The Fix") since her stage is basically a home away from home. This is the third time they have performed together on Taylor's tour. Here they are in 2013 on the Red Tour performing "Hey Porsche."

And here they are again in 2011 on the Speak Now Tour with "Just A Dream."