- "A teenage girl stepped into the living room at the bottom of the stairs. Oh, my God! Jennifer [watching through the slats of the louvered closet door] breathed in sharply. The teenager was the spitting image of Marty!"
- —From Back to the Future Part II by Craig Shaw Gardner (quote, page 69)
- "The teenager shrugged her broad shoulders. She was built sort of huskily for a girl, Jennifer thought, probably one of those high school athletic types."
- —From Back to the Future Part II by Craig Shaw Gardner (quote, page 70)
Marlene, like her brother, looked very much like her father. She appeared to like talking to her friends on the video telephone, and seeing her grandparents; she seemed to get along very well with her Grandma Lorraine in particular. Otherwise, little else is known about her personality.
In the normal timeline, after her brother was tried in a data-court and ended up going to prison for 15 years due to being involved with Griff Tannen's plan to rob the Hill Valley Payroll Substation, Marlene hatched a plan to break him out of jail. About a week after October 22, 2015 (the date of the robbery, at 1:38 a.m.), Marlene attempted her plan, but was caught and sentenced to 20 years in prison. Emmett Brown, visiting from 1985, found out about this and traced everything back to the afternoon of October 21, when Griff had convinced Marty Jr to join him. Doc headed back to 1985 to pick up Marty and Jennifer, who were just about to take a ride in Marty's new Toyota Hilux 4X4 and brought them to 2015.
In the revised timeline of the future, Marty pretended to be his son. By saying "no" to Griff, Marty managed to save his future family — Marty Jr. was now no longer involved in the robbery, and Marlene would not have to break him out of prison. Thus, both McFly siblings were safe.
Marlene attended the family dinner on the evening of October 21, where she was seen speaking to someone over her video glasses — possibly one of her friends. She was annoyed when her father asked her to pass the kelp tea, as well as when Douglas J. Needles, her father's co-worker, called a few minutes later, as the McFlys' only having one phone line meant she had to interrupt her conversation.
Behind the scenes
- Marlene's age is disputable — a draft script for Back to the Future Part II says she is 17 in 2015, like her brother, thus putting her year of birth as 1998. However, there is no mention of them being twins, and many fans think that she may be a year or two older than Marty Jr. due to the way she acts. She appears to be within the 20 year range.
- Being portrayed by a male, it is possible that Marlene is transgender because at this point in the timeline (October 21, 2015), the LGBT community has become more accepted by society. Had Marlene been born with the biological sex of female, she could have been portrayed by Elisabeth Shue, with the same applicable logic as all of the other characters. But since Marlene is portrayed by Michael J. Fox, it may be that she was actually born with the biological sex of male, and has transitioned into the gender of female.
- In the novelization, Marlene became severely depressed after the arrest of her brother and committed suicide.
- The voice of Marlene was actually provided by voice artiste Grey Griffin, who remained uncredited on-screen. This was achieved by redubbing Michael J. Fox's voice with that of Griffin in post-production. However, in the 2015 video game LEGO Dimensions, Fox provided Marlene's voice himself.
- Back to the Future Part II
- Back to the Future: The Card Game (Mentioned only)
- Back to the Future: The Game
- Back to the Future: The Game - Episode 2: Get Tannen! (Mentioned only)
- LEGO Dimensions
- Harold McFly (paternal medieval ancestor)
- Jennivere McFly (paternal medieval ancestor)
- Martin McFly (paternal great-great-great-granduncle)
- Pee Wee McFly (paternal great-great-granduncle)
- Seamus McFly (paternal great-great-great-grandfather)
- Maggie McFly (paternal great-great-great-grandmother)
- William McFly (paternal great-great-grandfather)
- Arthur McFly (paternal great-grandfather)
- Sylvia McFly (paternal great-grandmother)
- Sam Baines (paternal great-grandfather)
- Stella Baines (paternal great-grandmother)
- Milton Baines (paternal granduncle)
- Sally Baines (paternal grandaunt)
- Toby Baines (paternal granduncle)
- Joey Baines (paternal granduncle)
- Ellen Baines (paternal grandaunt)
- George McFly (paternal grandfather)
- Lorraine Baines McFly (paternal grandmother)
- Mr. Parker (maternal grandfather)
- Dave McFly (paternal uncle)
- Linda McFly (paternal aunt)
- Marty McFly (father)
- Jennifer Parker (mother)
- Marty McFly Jr. (brother)
- Marta McFly (grandniece)
| The McFly Family|
Marty McFly | George McFly | Lorraine Baines McFly | Jennifer Parker | Seamus McFly | Maggie McFly
Dave McFly | Linda McFly | Martin McFly, Jr. | Marlene McFly | Arthur McFly
| The Brown Family|
Dr. Emmett "Doc" Brown | Clara Clayton Brown | Jules Brown | Verne Brown | Einstein
| The Tannen Family|
Biff Tannen | Buford Tannen | Griff Tannen | Irving "Kid" Tannen
| The Strickland Family|
James Strickland | Roger Strickland | Irene Strickland | Edna Strickland | Gerald Strickland
Match, Skinhead & 3-D | Goldie Wilson | Douglas J. Needles