From StarWars.com:
"They can hardly be called "Star Wars Weekends" as we know them today, but Walt Disney World did stage two events in 1977 and again in 1980 that included at least one denizen from that galaxy far, far away -- Darth Vader.

After recently discovering a rare 1980 poster touting a weekend appearance by Vader at Walt Disney World Village, we decided to do a bit of digging online to see if we could find out anything more about the event..."
Check out Starwars.com for more.