The Molehill Highlanders
Old-timey string quartet appearing in the astoundingly long-running newspaper comic Gasoline Alley (it celebrated its centenary in 2018). The band consists of Gasoline Alley regulars Rufus and Joel (the guys who are usually shown riding in a mule cart) alongside some far less cartoony members. Given that GA artist/writer Jim Scancarelli is a fairly accomplished bluegrass fiddler, and given that he apparently played in a real band called Clyde Williams and the Mole Hill Highlanders in the 1960s/early ‘70s, it's likely the two other members (one of whom is named Clyde) are tributes to real bandmates. Still, since Rufus and Joel are included, we're counting this one.
Fake band connection: In the 22 April 2018 strip, the Highlanders play a song by the Three Blind Miceketeers.