"Background dancers" refers to performers who accompany and support the main artist or group during a musical or dance performance. They typically provide visual enhancement and add movement to the overall stage production. Full definition
Hey, look, it's a Robert Palmer background dancer. (mandatory.com)
Other times, Kelly says entire corps de ballet — essentially, the background dancers — would perish by fire. (racked.com)
Despite the number, the monologue did feel a bit off - beat with the funniest gag being his background dancers mimicking his every move as he performed his bits. (dailymail.co.uk)