Well, it's sort of approximately how it happened.
3 seconds sound clip from the The Muppet Movie (1979) movie soundboard.
You can hear this line at 00:03:32.288 in the Blu-ray version of the movie.
Quote context
[...]
- To the costume designers. To the prop makers.
- Speeches are not necessary, dear. Roll film.
- Yeah, but I'd like to thank everybody for all of their hard work and their patience, and their...
- Uncle Kermit, is this about how the Muppets really got started?
- Well, it's sort of approximately how it happened.
- Why are there so many songs about rainbows and what's on the other side?
- Rainbows are visions, but only illusions and rainbows have nothing to hide.
- So we've been told and some choose to believe it. I know they're wrong, wait and see.
- Someday we'll find it, the rainbow connection, the lovers, the dreamers and me.
[...]