Well, that was anti-climactic...he walks in the door, comes downstairs, takes one look at me, holds out his fist and says "Nice dress, bro".
We fist-bumped.
Shortly after that, once he made his dinner, he explained his non-reaction. Apparently, because he already knew I was kinda weird, he had been gearing up for something really out there as an explanation. In his words, I'm "Wired different. Very, hugely different. It's really obvious if you look for it."
All that worry over nothing, I guess...