Guillermo auditioned to be a part of the Stefani's Las Vegas residency on Monday after the singer announced that she needed more dancers.
"It's a big production, it requires big talent and when the notice went out, we sent in the biggest little ball of talent we know," Kimmel said about his on-screen security guard.
Guillermo stripped down to a golden tank top with the words "Rich Girl" written across it during his audition, a reference to Stefani's 2004 hit song of the same name.
Guillermo, despite being unable to keep up with the other dancers, was able to convince Stefani to recruit him due to his big heart and determination.
Guillermo's big moment then came during one of Stefani's Las Vegas concerts as the pop star allowed him to dance onstage in a banana costume during a performance of her song "Hollaback Girl."
"That went real bad," Guillermo said afterwards.
"Do I regret hiring Guillermo? Absolutely," Stefani added.
Stefani will be performing at the Zappos Theater until Nov. 2.