Andrew over at Puppetvision makes a very good point. Many people put The Dark Crystal (1982)(perhaps The Empire Strikes Back(1980)) as the first use of an animatronic puppet in film. But turns out it was probably another very innovative film — Mary Poppins. Walt was always looking forward an used animatronics in many of his films following Mary Poppins too.
Here’s a short video looking back at how that effect was made.
Here’s a little trivia for you: during the filming of that scene with the robin, Julie Andrews experienced shocks and burns from the electrical cords leading to the animatronic bird puppet.