I ask, because all three were seen in front of my layout at Doncaster show this weekend. Different people but each within an hour of the others.
My feeling - Star Trek. I mean it's not going to work you know. No matter how many times you hit the thing, you don't get to talk to anyone and if you keep talking to a plastic thing on your lapel, people are going to start edging away from you. At least the wearer wasn't in full Starfleet uniform I suppose.
On the other hand, a collectors club for modern toy trains doesn't seem groovy to me either.
Honourable mention: Red beard with 2 inches of growth below the chin bound with a couple of elastic bands like some sort of hair-based corn dolly. Bet there's a Lord of the Rings 8-disk DVD set at home waiting for another quick viewing.