Last year my wonderful, patient husband took charge of not only my own munchkin but 5 other children of other merchants during Steamcon. This year we decided to coordinate his costume with his cat herding activities, and I made him a Steampunk Pied Pier-esque outfit. I started with an old wool coat, tail'd it, and then covered it in patches using embroidery floss.
After the first few went on, I asked my husband if he thought it was too much and he told me it wasn't enough. Okay, then!
I also made him a hat with gramophone horns coming out of the back that we rigged with a bluetooth speaker so he could wander down the hallways playing music with kids following him dancing. Unfortunately the kids were all much more self-sufficient this year, and the hat turned out really heavy so he didn't wear it much. The only picture I got was after he'd traded it in for his more mundane, non-music playing topper.
He enjoyed the outfit, though, and that's what counts.