Gwen Stefani's 2016 show was made special with a surprise appearance by then-boyfriend Blake Shelton for a duet of his "Go Ahead and Break My Heart." Britney Spears' two Whoops... I Did It Again Tour shows during 2000 caught her at the height of her popularity, promoting her second album of the same name. Backstreet Boys have been back five times, while the Jonas Brothers' fourth visit in 2021 went on despite heavy rains earlier in the night. Pitbull made fans feel good three times, and Kesha made her Pine Knob appearance co-headlining with Macklemore during the summer of 2018.