Wondering where 'Johnson's' Mule came from, when "Old Thompson's Mule" was the original.
Ran across this verse in a Civil War minstrel song:

Den harness up de mule, be careful how ye whip
And mind your eye, Sam JOHNSON am de nigga gin'ral,
We're de brack brigade, Why don't ye let her rip?
Jeemeses Ribber Massa Greely, Oh!

"The Black Brigade," sheet music, words and music composed by Dan D. Emmett. Wm. A. Pond & Co., c. 1863. American Memory. "Sung with great success at Bryant's Minstrels."

I know that is really stretching it, but it caught my eye.