This episode aired on 3/24/1993 (after the holidays and before graduation) and focuses on Kelly turning 18 years old (Donna and Dylan have already celebrated their 18th birthdays). However, in Season 6, Kelly is the first of the group to turn 21 in September, prior to first day college classes.
During the dating game show when the announcer is calling the names of the guys, the second guy starts to stand up before his name is called.