This is the only TNG episode where a multi-person landing party is not made up at least one member that is 100% human. The landing party consists of Lt. Commander Data (android), Lt. Commander Troi (half Betazoid), Lt. Selar (Vulcan), and Lt. Worf (Klingon).
When Data refers to Wesley Crusher's "child like mind" Wesley responds by saying "Data chronologically you're not much older than I am". It is established that Data was constructed in the year 2336. As this episode takes place in 2365, this would make Data 29, which is at least 12 years older than Wesley.