Sheldon dressed up as Spock to go interact with kids at a birthday party. In The Codpiece Topology (2008) he did the same when the gang goes to a Renaissance Festival that he didn't want to go to.
The Star Trek Fan Club magazine that Sheldon receives in the mail is dated April/May 90 which dates this show in either April or May of 1990. Which has Sheldon still at 10 years old. Since his birthday is in February he will turn 11 in 1991.
The first episode since season one whose name has three items in it.