Karmin and Alexa Vega will also be on hand for the finale of season four, kicking off tonight at 8 p.m. on Nickelodeon.

Nick Cannon and Austin Mahone

Rushers, take note! Big Time Rush will kick off season four of their self-titled Nickelodeon series tonight (May 2), and they have some big-time stars stopping by before season's end.

MTV News can exclusively reveal that Nick Cannon, Karmin, Austin Mahone and Alexa Vega will all appear on the season finale, set to air later this season. Billed as the "Big Time Awards Show," the episode revolves around the Tween Choice Awards, where the boy banders are nominated and booked to close the show.

But before the foursome can take the stage, they uncover an evil plot to brainwash everyone in the audience. So BTR have to take down the bad guys and make sure the show rolls on as scheduled.

Ahead of the finale, Big Time Rush will invite singer/songwriter Gavin DeGraw to Thursday's season four premiere, which finds the group trying to fend off the invasion of a British boy band. (Paging former tour mates One Direction!) And if that isn't enough pressure, they hire a music manager to help them deal with some of the band's interpersonal issues. In true "BTR" fashion, wackiness no doubt ensues.

"Big Time Rush" airs Thursdays at 8 p.m. ET/PT on Nickelodeon, and this season will follow the guys as they record their third album and prepare for a world tour in a changing pop-music landscape. In some cases, art really does imitate life: On June 11, BTR will drop their real-life third album, 24/7, which includes their lead single, "Like Nobody's Around," as well as songs that will be featured on the show. Karmin will not only appear on the finale, but also on the release.

"The four of us have written most of the songs on the album and really focused on making music that everyone could listen to and enjoy," Logan Henderson said of the album. "24/7 shows a level of growth and maturity while still keeping the fun carefree essence BTR started with."

As if they didn't already have enough on their schedules, they will also hit the road with Victoria Justice this summer on the Summer Break Tour. It all kicks off June 21 in L.A. and will make 38 stops all across the country before wrapping up August 11 in Milwaukee.