At the Los Angeles premiere of “Star Wars: The Force Awakens” on Monday, fans, celebrities and droids mingled in celebration of all things intergalactic. But only one fan group was invited to send over 50 costumed fans to the event.

Clusters of stormtroopers standing in the bleachers near the red carpet were likely there with the 501st Legion, a “Star Wars” fan organization. Fifty-five members were invited by Lucasfilm and Disney to the premiere, Nicky Blum, the group’s events coordinator, said in a Facebook message.

The 501st Legion, formed in 1997, has more than 8,000 members around the world, with only two main qualifications to join: A fan must be over 18 and own a movie-quality costume “that is one of the bad guys,” Josh Mueller, the legion’s public relations officer, said in an interview.