The final episode of “Late Night with Jimmy Fallon” aired Friday night, something I won’t pretend to have known until a few minutes ago, and Fallon closed things out with a performance of “The Weight,” starring himself in the role of the late, Arkansas-native Levon Helm and with The Muppets filling in for the rest of the group. Anyone who caught the screening of Jacob Hatley‘s Helm documentary, “Ain’t in It for My Health,” the other week at the Ron Robinson Theater will recognize this as a tribute at the very far end of the taste spectrum, but there is something oddly soothing about it. It’s also not so far-fetched: according to Wikipedia, Levon was one of the original inspirations for Animal.