Let's talk about the first
Screen Songs and
Talkartoons produced by Fleischer Studios.
These shorts looked very different from what the Fleischers would later be known for; there are very few shades of gray, the drawings are very detailed, and the animation often comes off as stiff and limited.
Of course, things changed drastically when the studio brought in guys like Grim Natwick and Shamus Culhane to bring some looseness and outrageousness into the shorts, but I'm fascinated with this early era. I know that Roland Crandall and Sid Marcus animated on those shorts.
Here are a small handful shorts for reference:
Chinatown, My Chinatown Smiles Noah's Lark I've Got Rings on My Fingers In the Shade of the Old Apple Tree Radio Riot *
*The common print is off synch. This one is resynched.