 This was originally intended to be a straight film in the Invisible  Man series. After the huge grosses from  _Bud Abbott Lou Costello Meet Frankenstein (1948)_ (qv), the script  was rewritten to make it another thrill comedy with  Bud Abbott (qv) and Lou Costello (qv). As it happened,  Bud Abbott (qv) & Lou Costello (qv) met an invisible man in the  earlier film, too, but it was a different character.