Funnily, I suppose there's many people who know about Howard Johnson's serving clams, even though we know almost nothing else about the chain.

This is thanks to Zappa's song/musical story Billy the Mountain, prominently featuring Mark Volman and Howard Kaylan (the force behind The Turtles) on most memorable performances.

Excerpt:

    They left that night, crunchin' across the mojave desert
    Their voices echoing through the canyons of your minds
    "Ethel, want to get a cuppa cawfee?"
    
    "there's a Howard Johnsons! want to eat some clams?"
    The first noteworthy piece of real estate they destroyed was Edwards Air Force Base
    And to this very day, 'wing nuts' and data reduction clerks alike
    Speak in reverent whispers about that fateful night when
    Test stand number one and the rocket sled itself got LUNCHED!
    By a famous mountain-in and his small, wooden wife