In what some viewers believed to be an inside joke among the writers, the two Asian waitresses at Benihana are not the same two waitresses Michael and Andy bring back to the office. This "gag" was thought to play upon the racial stereotype that Asian people all look the same.
According to the blog of the propmaster of the show, the reason for the different actresses was because Andy and Michael failed to pick up the original waitresses, and all they could get were "less attractive ones".[1]
This is supported by the visuals; The waitress Cindy talks to clearly has blonde highlights, but neither of the waitresses who accompany Michael and Andy back to the Office have blonde highlights.
At Paley Fest 2007, Greg Daniels admitted that the joke failed due to poor casting. The waitresses that come to the office were too attractive.[2]
Closed Captioning on the episode contradicts the prettier/uglier waitresses story about switching actresses. As Michael's party date wheels the bicycle out of the party, the CC displays "[Cindy] Merry Christmas." Cindy was the name of the original "pretty" waitress.