The episode starred Cliff Robertson (who most modern cinema fans will recognize as Tobey Maguire’s Uncle Ben in the Sam Raimi “Spider-Man” movies) and if they were going to sell the nightmare-inducing final reveal that the ventriloquist dummy had swapped places with the handsome star, then they were going to need to make the human look like Willy the Puppet and the puppet look somewhat like Cliff Robertson.
Rod Serling and his crew didn’t have anyone on staff that could handle that, so they ended up recruiting for an unlikely source: Walt Disney Animation.
As the story goes (at least according to 1992’s “The Twilight Zone Companion” written by Marc Scott Zicree), “Twilight Zone” makeup effects artist, William Tuttle was hard up for ways to pull off the effect in a way that would please Serling, who was determined that the gag only works if the audience can recognize Robertson in the dummy at the end. It still had to look like a real ventriloquist’s dummy, but have enough of the actor’s features so nobody walked away from the episode confused.
Tuttle had the mechanics of the prop covered but needed someone talented in caricature to design the face. One short consult with “Twilight Zone” production manager Ralph Nelson resulted in the name T. Hee.