Tomco

Tomcois a slash ship between Tom the Demon and Marco Diaz from Star vs. the Forces of Evil.

Canon Relationship
Tom and Marco know each other through Star Butterfly, Tom's ex-girlfriend and Marco's best friend. They first meet each other in Blood Moon Ball, the 15th episode of the first season, when Tom invited Star to a demon prom event. Initially, they disliked each other, with Tom jealous of how close Marco is to Star, and Marco suspicious of Tom's intentions. However, in Mr. Candle Cares, the third episode of the second season, the two bonded after Tom kidnapped Marco to try and get information out of him. After a short talk about their thoughts on Star, Marco gives Tom some sound advice and, knowing that Marco is right, Tom takes him home. After his talk with Marco, Tom sincerely apologizes to Star for his actions. At the very end of the episode, Marco admits that Tom is "not so bad".

Next, Friendenemies, the 19th episode of the second season, dedicated an entire episode to the two of them. Marco is suspicious when Tom seeks his company instead of Star's, but relaxes after the two of them share mutual interests. One of which is a love of the fictional band Love Sentence, and the two showed it by singing two songs and having a friendship marathon. Although the episode got shaky at the end, Tom managed to make it up to Marco and the episode ended on somewhat good terms.

Afterwards, in Naysaya, the 26th episode of the second season, more of their relationship is elaborated upon. Marco goes to Tom because he believes the demon put a demonic curse on him, and Tom admits it was him and that he was sorry. When prompted why he would do that, Tom said it was before they started hanging out. Then he proceeds to chide him about not asking anyone out since the events of Blood Moon Ball.

Evidence from the show and from Disney XD's #MarcoLIVE animated chats point to a stable friendship based on mutual respect, with Marco referring to their relationship as "friendenemies" on #MarcoLIVE. According to Marco on the animated chat, he views Tom as a unique guy, and is both surprised and happy that they get along so well.

Fanon Relationship
Note: This list is not to be considered all encompassing, and is both trend and opionion-based from what the author sees of the fandom. If you have grievances with the content of this section post a comment in the discussion section below, and if you wish to add to it then append to this section as you see fit.

Online polls rank Tomco as the second most favorable ship, with Starco (Star and Marco) comfortably ahead. The distance between Tomco and the rest of the ships is rather sizable, making Starco and Tomco the two leading ships of the series. Tomco shippers also seem to ship Janstar (Janna and Star), possibly because they are both LGBTQ+ ships and/or they feel a need to pair Star with someone (not to say Janstar isn't a ship in its own right). When asked, some Tomco shippers said they feel Star and Marco are just really good friends, and the #MarcoLIVE chat reflected this to a degree.

The two of them occasionally share moments that two boys generally don't have. For instance, they have a "couple's song" of sorts, which is a duet they sang in Friendenemies. The song is even referred to as "our song" by Marco on the #MarcoLIVE chat. Before that in the same episode, they sung another, more upbeat Love Sentence song in a fun friend bonding montage of sorts where they danced around and had an awesome time. Marco and Tom also got into a photobooth and posed for some somewhat unconventional pictures. Speaking of unconventional pictures, the image on this wiki is provided by the show and is an official promo poster for the episode Friendenemies which quickly became notorious among fans for depicting the two like a couple on the cover of a romance novel. But most of this could be explained away as a progressive aspect of the series, as Star and her friends seem to eat gender norms for breakfast.

Trivia

 * It's worth noting that in Friendenemies, Tom appears eating an ice cream cone that has the colors and pattern of the pansexual flag. What makes this worth noting on a shipping wiki is that the part he is licking is red, similar to Marco's hoodie, and seems to have a pink heart in it.