“First Drafts of Rock†is among Jimmy Fallon’s most underrated recurring segments, and on Monday night he brought it back, getting Kevin Bacon to play Tom Petty in an exploration of the earliest version of Petty’s 1989 hit, “Free Fallin’.†You know that line about how the “good girl†who “loves her mama†also “loves horses and her boyfriend, too� To hear Bacon and Fallon tell it, the original draft of the song went way deeper into that girl’s interests. Turns out, they’re pretty specific.