Thanks Orthar, great work.
With a bit of googling have found the official Lucas back history from StarWars.com (wonder why I couldn't find this earlier, doh!). Seems Joe Johnston was mostly responsible for the design, and the parade was indeed the first public outing for the character:
http://www.starwars.com/episode-v/bts/a … index.html
That means the chronological history is:
Parade, 'Holiday Special' TV, toy, public appearances, 'Empire Strikes Back' film.