Football is BMO's imaginary friend. She is BMO's reflection and exists wherever BMO has a reflection. Throughout her appearances, BMO teaches her what it's like to be alive.
Football is first introduced in the episode "Five Short Graybles," she introduces herself to BMO in the bathroom mirror. She then asks BMO to show her what it's like to be alive, which BMO happily agrees to, showing her how to use a toothbrush, how to use soap, and what it's like to pee.
In the episode, "Five More Short Graybles," BMO reveals that Football has come along way through his teachings, but still has so much to learn. BMO then proceeds to teach her about kitchen appliances and how to position her pinky.
In the episode Football, repeats over and over how much she loves BMO. She then reveals to BMO that she wishes that she could be in the real world. They then proceed to switch places and Football is able to experience the realness of the world. After she realizes how good it is in the real world, and how lonely it is in the mirror, so she tries to steal BMO's body. At the end of the episode, after being haunted by the reflection of BMO, Football falls into the water and realizes how much she likes living in the reflection of the lake. Before BMO returns to land, Football tells him that she still loves him and hopes that he will continue to visit.
- "The Orb"
Football appears to look exactly like BMO except in reflection form. Plus, she is mostly left-handed while BMO is mostly right-handed.
Football has as much curiosity and joy about the world as BMO does. However; in the episode "Football," it was revealed that Football aches to live in the real world like BMO, so that she may experience the same love and feelings as BMO does.
- While Football is seen as her own separate being in BMO's eyes, she is generally treated by Finn and Jake as a figment of BMO's imagination. It is never outright confirmed to what extent she exists.
- In the episode, "Football," Jake asks if BMO is Football's "lil’ Papa," to which she giggles and bounces around.
- In the episode, "Football," Football reveals that life behind the mirror is "cold, empty, and lonely."
- While she was formally introduced in "Five Short Graybles," her appearance in "BMO" shows that she existed before the events of Adventure Time.