Sparrow began his career as a stand-up comic and entered films in 1964, in Dr. Terror's House of Horrors. Subsequent films, interspersed between countless TV appearances, included the 1969 sex fantasy Zeta One, Young Sherlock Holmes, and the acclaimed 1988 film The Accidental Tourist (with William Hurt and Geena Davis). He enjoyed a resurgence in the 1990s, with key roles in Robin Hood: Prince of Thieves (as blind retainer Duncan), The Secret Garden (as gruff gardener Ben Weatherstaff), the American film Now and Then (as tragic drifter Crazy Pete), and Prometheus (as Granddad, an ancient miner engaged in an argument with the Greek god Hermes).