Charles Nichols and Nick Nichols were the same person, Charles was his real name, though most who knew him called him Nick.

00:00-00:02 - Norman Tate / Shamus Culhane (?), George Rowley (FX)
00:02-00:12 - Norm Ferguson, George Rowley
00:12-00:16 - Norm Ferguson, Charles Nichols, George Rowley
00:16-00:22 - Norman Tate / Shamus Culhane (?), George Rowley
00:22-00:24 - Charles Nichols, Norm Ferguson, Ed Aardal (FX)
00:24-00:29 - Norman Tate / Shamus Culhane (?), George Rowley
00:29-00:33 - Norm Ferguson, George Rowley
00:33-00:41 - Hugh Fraser, Norm Ferguson, George Rowley
00:41-00:48 - Charles Nichols, Norm Ferguson, Ed Aardal

Iirc, this scene is where most historians have identified as containing some potential Culhane animation