When Amos 'n' Andy was a radio show, the main roles were played by the program's creators, Freeman Gosden and Charles Correll. For more than thirty years, these two white guys played beloved black guys on the radio.
In 1951 when it came time to turn it into a TV show, Gosden and Correll stepped aside — what else could they do? — and cast the series with black actors — or "colored people," as they were then called. This was quite a big deal at the time because America loved Amos, Andy and their cronies on the radio, which meant that Gosden and Correll had to convince the viewers that the characters wouldn't be ruined; that they'd still be the same, popular folks. (Another reason that the characters couldn't change is that Gosden and Correll were continuing to do them on the radio, though for a declining audience.)
To this end, the first TV episode started like this. It runs about five minutes and it's Gosden and Correll introducing the actors to an audience that came in to watch the first show and to have their laughs recorded. (This is all explained in a graphic at the beginning.) The casting was actually quite good…especially Tim Moore, who played the Kingfish and stole every single scene in which he appeared. So changing actors wasn't a problem and the show did rather well in the ratings. The problem, which caused it to be yanked off the air after two years, was that the nation was changing in its attitude about minorities, and a lot of folks weren't happy with how the show depicted blacks. The series stopped production at the end of its second season and had a checkered presence in off-network reruns for a short time before disappearing completely.
Here's the film of Gosden and Correll introducing their players. Unfortunately, it doesn't include the explanation that they gave the audience about why they were recasting the parts. We all know why they did it but it would be interesting to hear the phrasing and the rhetoric they used.