Madonna has even caught onto the 'Psy syndrome'.

Yesterday at Madison Square Garden, Madonna held a concert in which Psy appeared as a guest.

Madonna performed a remix of her song, "Give it 2 Me" and "Gangnam Style." While the song was playing, Psy made an entrance and the two dance together.

With the surprise appearance of Psy, the crowned went wild. Everyone dance along to Psy's "Gangnam Style" as well.

This performance is now uploaded onto YouTube and is gaining much attention online.