Tom Corboy's "Mondo Elvis" (1984) is a short, award-winning, and oddly unsettling documentary about extreme Elvis Presley fanatics after The King's demise. From the description at Mondo A-Go Go Video's channel:
"This award-winning film takes a searing look at Elvis Presley's most fanatic followers. Meet such devoted disciples as the twin sisters who believe Elvis was their father, a woman whose husband divorced her for excessive devotion to Elvis, and an impersonator who claims The King came to him in a dream.
Disturbing yet entertaining, haunting yet hysterical, this program is a must for anyone interested in comprehending the significance of America's greatest cultural hero."
(via r/ObscureMedia)