When Jefferson was chained, the other slaves also chained there sing the song "When the sun comes up, And the first quail calls, Follow the drinking gourd. For the old man is a waiting, For to carry you to freedom, Follow the drinking gourd". Folklore has it that enslaved people in the United States used it as a point of reference so they would not get lost. The was was collected from the folk tales and was first published in 1928. The Drinking Gourd is another name for the constellation of Big Dipper in the northern skies, which has two stars always so aligned that they point to the Polaris or the North Star. Thus, all slaves had to look for the Drinking Gourd and follow it to the North Star to go north to freedom.
When Ray is discussing what to do with Mick the Zombie to Martin, he refers to him as Marty (A tribute to Back to the Future).
A Scrimshaw is scroll work, engravings, and carvings done in bone or ivory. That was what Jefferson was doing.
Just as Ray is going to inject him with the Zombie cure, Mick calls him by his full given name, Raymond, instead of his usual "Haircut". One of the few, if not only, times Mick has done this.
General says "What in perdition's flames is a zombie"? Perdition is hell, so perdition's flames mean Hell's Fire. He used it like a swear word or exclamation.