I got paid to be in a Dog costume one summer. I didn't get to ride on a roller-coaster or anything, just walk around Wellington waterfront, (it was a publicity thing for the Wellington Museum of City and Sea.) I was "Paddy the Wanderer" who was kind of an icon round the waterfront in the depression era. I got paid fairly well and since the visibility of those things is very limited coupled with walking around in a public place I had someone to go around with me, (who had to do all the real work, talking to people, handing out fliers etc.)
The kids mostly liked me or were scared of me, the other lot felt it would be fun to kick or confuse me, (easy thing to do, heat + lack of visibility = confused dog.)
When I was at the museum during this 'employment' though there was this kid's dinosaur show, and the guy who was meant to be in the Dinosaur costume didn't show up. As the resident animal-costume-wearer I was required to put this thing on. It was heavy as hell, uncomfortable, could see even less than with the Dog head on, it had a fan in it so I wouldn't overheat and yeah again, it was heavy as Hell. I almost broke my damn neck with that bloody head on. I have a new found respect for Barney the Dinosaur.
I imagine your brother would have a costume more like the Dinosaur one I had to wear - more professional. I hope it's more ergonomic than that fucking Dinosaur, otherwise I have to say your brother's job sucks and he'll be paying chiropractors a lot of money in coming years.