The Bob Pickett who plays the actor that goes off with Elly May is indeed the same Bobby "Boris" Pickett who recorded the iconic Halloween hit "Monster Mash."
"General Grant," refers to General Ulysses S. Grant, who led the United States/Union army to victory in the American Civil War (1861-65). After the war he entered politics and was the Republican Party's candidate for president, winning the election and served as the 18th president from 1869-77.