William McFly in 1931B.
William Sean McFly
Biographical information
Date of birthApril, 1885
Age (1885)0 (born)
Age (1931)46
Age (1955)70
Age (1985)100 (Deceased)
Physical description
Hair colorBrown
Grey (1931)
Eye colorBlue
Behind-the-scenes information
Played byUncredited baby actor
Voiced byMichael J. Fox (2010 video game)
" Doc turned his attention to a file of his own, and came to somebody else who looked familiar — a man in his mid-twenties who bore a resemblance to Marty. The picture came from the early 1900s, a little later than what they were looking for, but the man was surrounded by his family, including an older man — his father, perhaps? — who was dressed as a farmer. / "Look," Doc pointed out. " 'William McFly and family.' Your relatives?" / Marty nodded. "Yeah. I think my great-grandfather was called William—" He glanced at the photo. "Nice-looking fella." "
—From Back to the Future Part III by Craig Shaw Gardner (quote, page 29)
"Maggie stood by the cradle, rocking a baby in her arms. The baby's crying was softer now, and stopped every now and then for the infant to catch its breath. / Maggie smiled at Marty as he walked closer. / "This here is William Sean McFly. Aged five months. He's the first of our family to be born in America." She glanced down at her baby. "It's all right, Will. This is Mr. Clint Eastwood here, visitin'." / The baby looked up at Marty and smiled. / "Sure'n he likes you, Mr. Eastwood," Maggie said. "
—From Back to the Future Part III by Craig Shaw Gardner (quote, page 51)
"So you're my great-grandfather. The first McFly born in America. And you peed on me."
—Marty to William

William Sean McFly (b. April 1885)[1] was the Irish-American son of Seamus McFly and Maggie McFly, nephew of Martin McFly, the father of Arthur McFly, the paternal grandfather of George McFly and the great-grandfather of Marty McFly. He was the first McFly born in America.

Normally, William did not get along with strangers; however the infant took an instant liking to his future great-grandson Marty McFly (under the alias of "Clint Eastwood") when Marty journeyed to 1885 and visited the McFly family farm.[2]


William was seen earlier fully grown in a photo with relatives in the book A History of Hill Valley, 1850-1930 where Marty noted he was a "good-looking guy". Since William and his family were featured in the book, he might have been a prominent citizen and played a role in the growth of the town.[2]

William McFly baby

Baby William McFly in the arms of his mother.

"Wait, that was Great Grandpa Willie! I met him when he was a baby! He peed on me."
—Marty, after just meeting an adult William

In 1931, William worked for Hill Valley Mercantile Deliveries. He came to the Hill Valley High School on October 13 after hearing that Arthur had getting hitched to a "Canadian floozy." At first he disapproved of their marriage, but changed his mind upon meeting his son's wife Sylvia.


William McFly in 1931

William briefly talked to his future great grandson, Marty, thanking him to stay out of McFly family business. Then William paused for a moment with a mildly bewildered look on his face, as if sensing something vaguely familiar from Marty. William quickly shrugged this off and went back about his business.

In 1931B, William worked for Haysville Mercantile Deliveries and was driving through what had once been Hill Valley on October 13. He pointed Marty and Doc Brown to the house of an old lady named Mary Pickford (who in truth was a time lost Edna Strickland). Edna confessed to Marty and Doc that she destroyed Hill Valley. She was about to shoot them when William arrived to cover their escape by grabbing her and her shotgun, telling them to get away. William's fate after 1931B is unknown.[3]

Behind the scenes[]


Photo of William McFly and his family


Close up of William from the McFly Family photo.

  • In the photo from A History of Hill Valley, where a middle-aged William McFly is seen with his family, including his parents, Seamus and Maggie. Like Seamus, William is portrayed in the photo by Michael J. Fox as well. Bob Gale notes in commentary to Part III that the art department included "two Michael J. Foxes and two Lea Thompsons" in the picture.[4]
  • Coincidentally, actor Cliff Robertson portrayed a character named "William McFly" in a 1967 film.
  • William is the only one of Marty McFly's direct paternal ancestors not known to have had a quarrel with someone from the Tannen family.
  • What William McFly's supposed contribution may have been is not hinted at. It is possible that Marty's principal at Hill Valley High School, Stanford S. Strickland, might not have been aware of this when he proclaimed that "no McFly ever amounted to anything in the history of Hill Valley" in 1985. This occurred in the unaltered timeline. When Marty McFly altered history from 1955 onwards, Strickland might not have said this. A likely explanation is that the McFly family picture is simply there because they were early town inhabitants, and never actually did anything noteworthy otherwise. However, it is also possible that the McFlys simply never amounted to anything only according to Strickland's personal standards, which are likely to be impossibly high.


Notes and references[]