He and Gabby are the only humans to appear in the whole show (until Santa Claus in the two Christmas episodes and Commander Megan first seen in Robots in Space). Judging by his skin tone, AJ might be Caribbean or African.
It's a versatile piece that can add a touch of sophistication to a casual outfit. 100% There is absolutely no reason why you should feel reluctant to wear a blazer when you're out with friends.