There was no red carpet at Thursday night's London premiere of "X2," the sequel to "X-Men."

Instead, there was a blue carpet, in a nod to the movie's mutant skin tones, PEOPLE reports. More than 3,000 eager and curious fans jammed behind galvanized steel crash barriers outside the Leicester Square cinema throughout the afternoon leading up to the evening premiere.

"It's so hard to believe that people would be this excited," said Shawn Ashmore, 23, who plays the chilled-out character Iceman. "What I'm thinking is that I really hope I don't trip up and look really stupid."

"I'm very shy, and don't like it when people see me on the street and yell 'Rogue!'," said movie costar Anna Paquin, 21, who plays -- that's right -- Rogue. "But it's really flattering for thousands of people turn out like this to see us go party."

Rebecca Romijn-Stamos, 31, who plays Mystique, added: "I'm a little shaken up. I've never seen anything like this. The queues seem to go on for miles. It's a little intimidating."

She and actor Alan Cumming both had to endure hours in the makeup chair to get their blue skin. Cumming, 37, who plays the creepy Nightcrawler, revealed, "You get up at about two in the morning to have it put on. It isn't pretty."

He also recalled telling costar Halle Berry, who plays Storm, "that if we ever got together we'd make black-and-blue babies."