We sat down to watch the original TRON released in 1982. To our surprise there is a Hidden Mickey in the film!
About 3/4 into the movie when the Solar Sailor is gliding across the grid, look for Mickey in the landscape!
An added surprise! On the bridge of Sark's battle cruiser there is a diagram. On the right you'll see and hear Pac-Man, "womp womp!" ;)