After Ashlee Simpson and Christina Ricci attended his Fashion Week show, designer Richard Chai celebrated Thursday by busting dance moves at a Mister H after-party. Chai was seen hanging with designer Phillip Lim, spies said, but “the moment TLC’s ‘No Scrubs’ started playing . . . Richard started dancing and singing.” He was also toasted with rounds of cocktails. Chai told us, of having a show on Fashion Week’s first day, “I used to hate being first . . . Now I appreciate it and get to my friends’ shows.”