1987: Adventure Boy Ponies
QUARTERBACK
Blue shire pony with blue mane and tail (white streak in mane), magenta and white rugby ball (or american football) symbol.
To me, Quarterback is the all-American Adult Boy Pony. With his helmet, his symbol and his name, he's obviously meant as an advocate of American Football - though in many UK auctions you might find his symbol described as a rugby ball (since it's the closest thing we have in these parts!)
Quarterback, oddly, did not change his name between editions - despite the obviously American nature of his identity. Like Tic Tac Toe and Cotton Candy, he is one of the ponies that drops the hint as to the origins of the toy line.
I don't remember Quarterback being a very prominent figure in the pony comics. Aside from the story where Princess Ruby, in one of her restless rampages, manages to stumble across the boys, I don't even remember him playing a part. I guess he must have done - but whatever it was, it wasn't overly memorable :S
Quarterback was not brought back as part of the second set, and was only sold as one of the original six, making him one of the more difficult to find Adventure Boy/Big Brother Ponies.