Regis and Kelly always do it up big for Halloween. This year, 'Live!' is kicking off their annual Halloween Headliner's Ball spectacular (airs Mon., Oct. 31) with a flash mob production number, and we've got the exclusive first look right here.

Featuring Kelly Ripa (in some fabulously bright purple lycra pants) and guest co-host Nick Lachey (not sure we'll say the same about his fluorescent shutter shades), the choreographed dance to LMFAO's 'Party Rock Anthem' has more than 100 flash mobbers dancing, all for a confused crowd of onlookers in New York's Lincoln Center.

Back in the studio, 'Project Runway' host Heidi Klum, '90210' star AnnaLynne McCord and 23 other celebrity guests will be on hand for the show as Kelly and Nick re-live this year's biggest headlines and most outrageous shows through costume -- almost 40 different looks in total throughout the show -- from 'Toddlers & Tiaras' to Charlie Sheen and everything in between.

And, of course, the audience members will be dressed up for the costume contest as well -- one lucky person will win the grand prize of $10,000 to shop at HomeGoods.

Watch the entire flash mob cold open now to get you in the mood ...