They Painted a Whole Set Sepia for The Wizard of Oz
There's a reason "We're not in Kansas anymore" is the most cliche way to announce that things have gotten freaky, and that's because the transition from sepia Kansas to Technicolor Oz in The Wizard of Oz is one of the raddest moments in movie history. I know it's weird for a straight 20-something guy to publicly ramble about the infectious wonder of a 1930s musical, but I don't care. It's still a great bit of cinema, a transition that wouldn't be possible in any other medium, simultaneously celebrating the magic of youthful imagination and cinema's constant technological march toward telling bigger and better stories.
"Also, the act of crushing people with houses and stealing their shit."
But ironically, the transition itself didn't use any kind of fancy technology at all: Instead of using clever editing techniques, the Wizard of Oz crew just painted an entire set sepia. Bobbie Koshay, Judy Garland's body double, stood in for Garland (again, completely covered in sepia paint) and allowed Garland to take her place after the camera moved into Oz by stepping out of frame for just a fraction of a second.
That's the thing about these old movies: They don't have that "How did they do that?" element -- we know that the Cowardly Lion is just an actor in a costume, the Tin Man and Wicked Witch are just actors covered in toxic paint, and the Scarecrow is just a guy trying to figure out his sexuality.
"Some people go "both ways!". We got you, Scarecrow.