[tzs]

There have only been two copyright extensions that affected the copyright on Mickey Mouse, and I haven't been able to find any significant Disney involvement with the first one.

The first one was when the Copyright Act of 1909 was replaced with the Copyright Act of 1976. Between 1909 and 1976 there had been a lot of changes in technology, such as the rise of radio, TV, movies, and computers, and it was widely agreed that the 1909 Act was not up to handling it. Also international distribution was more common, and most thought the US needed its copyright law to be more compatible with the rest of the world. The 1976 Act started that harmonization (although it left a lot of it for the Berne Implementation Act of 1988).

The second was the Copyright Term Extension Act of 1998. That one Disney was a significant force in its creation and passing.

[kevinmchugh]

The 1976 act was also useful in settling the idea of a "work for hire". There'd previously been a lot of bespoke, confusing contacts and promises made around ownership of IP and the 1976 act settled it. It didn't make artists who'd been ripped off (Siegel and Schuster) whole, but it cleared up delineations. This paved the way for future artists to actually know what they were seeking, and keep some of the good stuff for themselves