Olivia Newton John and John Travolta just dressed up in their Grease costumes This sweet yellow party dress was first seen in the 1978 , where actress Didi Conn wore it as Frenchie. After that, the dress very likely went into rental stock, where it This sweet yellow party dress was first seen in the 1978 Grease, where it was worn by actress Didi Conn as Frenchy. After that, @recycledmoviecostumes on Tumblr periodedits : Olivia Newton John as Sandy Olsson GREASE (1978)