Relationship with Friends

Finn and Jake
BMO lives in the Tree Fort along with Finn and Jake and is used as their game console and many other things. It is loyal to Finn, as it said it will kill anyone who tries to hurt Finn, as seen in "Incendium." Also seen in "Video Makers," BMO does not side with either Finn or Jake. BMO cries when Finn shaves off his hair to be "Davey," sobbing that his "beauty" is destroyed.

Marceline
It seems that Marceline and BMO have a fairly friendly relationship, as she is seen playing it in "Evicted!" and commenting on how she thinks it is cute. Also in "What Was Missing," Marceline assists BMO and proceeds to call it "baby." 

Lorraine

In "BMO Noire," BMO mentions that Lorraine is "red hot like pizza supper." Furthermore, Lorraine also mentions that the loot is in their "secret grown up kissing spot" at the end of the episode, thus implying that at one point in time they had a relationship. This might be taken as an indication that BMO finds Lorraine attractive. However, the entire episode hints that the plot of "BMO Noire" is nothing but a play created by BMO's imagination. So, it is possible that their relationship exists only in BMO's fantasy. It is also possible that BMO is not attracted to Lorraine and the attraction/relationship is fictional like the detective persona that BMO created for itself.

Football
Football is BMO's reflection in the mirror or window or whatever it can see its reflection in. BMO tells Football about all of the things in the real world and tries to educate Football on how to act and what things are in the world so that when Football grows up she will know what to do. BMO does this to keep it from feeling lonely whenever Finn and Jake are away. Football appears in the "graybles" episodes, "Five Short Graybles" and "Five More Short Graybles." Air (Bubble)

 

Air (Bubble)
Air (Bubble) is a pal that BMO met in the episode "BMO Lost." After an adventure to help BMO get home through hard times with a baby named Sparkle (whom BMO had named Ricky), Bubble confesses that it is in love with BMO and proposes they get married, which BMO gladly accepts. Sadly, Jake decided to pop the bubble, making it now Air. 

Sparkle (Ricky)

Sparkle (Ricky) appears in the episode "BMO Lost." This baby was lost and separated from his mother, so BMO decides to name the baby "Ricky" and bring him along on the adventure of all three characters, BMO, Air (Bubble), and Sparkle (Ricky), trying to find their home. Sparkle is later rediscovered by his mother and taken to his rightful home.

 

Moe
Moe is BMO's creator, as shown in the episode "Be More." He created BMO because he wanted BMO to take care of his son, but he "never ended up dating any women." Moe created BMO so it could "Be MOre."

Trivia

• BMO's voice was originally much deeper. Pendleton Ward revealed this on the animatic for "Rainy Day Daydream" on the Adventure Time: The Complete First Season DVD box set, which is also heard in the animatic.
• BMO can display emoticons on its screen, as seen in "What Was Missing."
• BMO's screen can be used as a touch screen for at least one function, Jake demonstrated this in "James Baxter the Horse."
• When BMO lowers its volume in "Holly Jolly Secrets Part I," it puts its volume on the lowest setting but could still talk.
• Many of BMO's games are knock-offs of the games for the Atari 2600 video game platform.
• According to "What Was Missing," BMO's prized possession is its controller.
• In the special features section of the It Came from the Nightosphere DVD, BMO's age is shown as "VER. 2600," and its species is "110 VOLT/60 HERTZ SYSTEM." BMO is also referred to as "she."
• During Pendleton Ward's interview with Hot Topic, he stated BMO is his favorite character.
• BMO supposedly has "butt circuits" as mentioned in "BMO Lost." 
• As seen in "James Baxter the Horse," BMO can cry, and its tears are apparently triangles.
• It was revealed in "Shh!" that BMO's favorite song is No Wonder I by the band LAKE.
• BMO is completely the same in the Fionna and Cake version.
• BMO is Moe's favorite robot.
• BMO literally has a heart of gold, as seen in "Be More."
• It was revealed that in the episode "In Your Footsteps" BMO plays soccer.
• BMO's BMO chop memory (which originated from "Card Wars") was deleted in "Be More," implying that we may never see it again.

                                      
                                      
                         

Personality and Traits

According to Finn, "BMO does weird junk when no one is around." He proves this in "Five Short Graybles," where BMO talks to its reflection in the mirror, naming him Football, and pretended to be a "little living boy." In "BMO Noire," BMO acts out a film noir fantasy complete with giving names, voices and dialogue to a number of animals and an inanimate object in the house. The way it interacts with its reflection in "Five Short Graybles," as well as the animals in "BMO Noire," is evidence that BMO may suffer from dissociative identity disorder, otherwise known as a multiple personality disorder. This causes BMO to act like completely different people, and have them communicate with each other.

BMO claims to not have emotions, but this is not true. In "Donny," BMO says, "I am incapable of emotion, but you are making me chafed!" It shows signs of annoyance in "Too Young" when Jake uses BMO as an ottoman. BMO demonstrates independence when it refuses to turn down its music even after Jake tells it to. Although they are both robots, BMO refuses Neptr's request to hang out more in "BMO Noire" by saying, "No, Neptr, I am not like you." In "Davey," BMO cries while Finn shaves his head to disguise himself as We Fixed a Truck"

Who is BMO?

BMO (phonetically spelled Beemo) is Finn and Jake's living video game console, portable electrical outlet, music player, roommate, camera, alarm clock, toaster, flashlight, strobe light, skateboarder, friend, soccer player, video editor, video player and Chef.

BMO looks like a half-Macintosh half-Game Boy Color with Atari 2600 controllers. It also shares some traits with a Vectrex.

BMO is a medium-sized blue-green handheld gaming device, sometimes appearing with one or two controllers attached to it. When it is not being played it has an 8-bit face.

BMO's front includes an arrow pad, a floppy disk slot, multiple different shape buttons, two controller sockets, and of course the face, or screen. There is also a compartment with a red button hidden underneath the yellow D-pad. His software is somewhat similar to a Macintosh computer, as seen in "Be More" with a graphical interface and drag-and-drop file manager.

It makes its appearance in the title scene of the Theme Song of every episode of Adventure Time, just as Finn and Jake pound their fists together. BMO is characterized as a loyal, trusting, and helpful friend who is protective of Finn and Jake.

(http://adventuretime.wikia.com/wiki/BMO)