Mr. Triangle/Relationships

===Greysnow===
In the first two seasons of the show, Mr. Triangle used Greysnow as a puppet of sorts, as a means to go through with the evil plans his boss told him to go through with, While the two didn't really interact apart from one occasion in "Pride", Greysnow seemed to hate Mr. Triangle as much as the other snowtabs did, if not more. In "Chase Against Time", Greysnow and Mr. Triangle are finally separated from each other, by the help of Tabsnow. In the same episode, Greysnow attempts to redeem Mr. Triangle in order to see if it'll work so they can all escape the voids, as revealed in the next episode, while it doesn't work right away, from moments since that redemption attempt, Mr. Triangle seems to have gained a conscience, as he starts questioning his motives and while still on the path of being evil, at least takes notice of the fact that he's doing bad things, using Greysnow's possession as an example. In "Reflection", Mr. Triangle goes to Greysnow and apologizes for his wrong doings, to which Greysnow surprisingly accepts and decides to help him get through to the other snowtabs as well, which eventually works out, it's also worth noting that Greysnow is the first of the snowtabs to actually refer to Mr. Triangle as a "friend", which shows that the two have an immediate click with each other. In "Tri Hard", Mr. Triangle refers to Greysnow as his best friend, and Greysnow reciprocates this, and is also the driving force for Mr. Triangle to realize he is worth something, due to his major reason for being evil being his sense of worthlessness.
===Snowtab===
During the first three seasons, Snowtab is the guy who hates Mr. Triangle the most, and is the last one of all the characters to forgive him when he is eventually redeemed. Mr. Triangle desperately tries to make it up to Snowtab during this time, but it doesn't work until Mr. Triangle sacrifices himself in order to save the Snowtabs from being killed by The Ruler of Universes. After "Tri Hard" they have barely interacted, but it is implied that they have stayed friends after the events of Tri Hard.
In "Eye, Roommate", Snowtab and Mr. Triangle become roommates, leading to their friendship becoming much stronger.
===The Ruler of Universes===
In Season 3, The Ruler of Universes serves as Mr. Triangle's boss, the driving force behind Mr. Triangle's villainous actions in the series thus far, after failing in "Chase Against Time" and "The Exorcism of Greytab", Universes locks Mr. Triangle in a cage in order to understand the meaning of his failures, while locked in this cage Mr. Triangle is able to think, and eventually he plans to escape the cage and join the Snowtabs, effectively rebelling against his boss, which works.
Eventually in "Tri Hard", Mr. Triangle is reunited with his boss, and is killed for rebelling against him, until Gingtab and Tuxtab use the DeLorean to save him of course.
During Season 4, Mr. Triangle only sees The Ruler of Universes once, in "Unpresidented Fate", and in "The Father-Son Project", we learn that Universes forced Mr. Triangle to spend less time with his son, leading to their more distant relationship.
The two don't cross paths all too much up until "Gregory Triangle" and "The Battle of the Bootes Void", where the two finally resolve their issues, albeit not on good terms, but moreso them coming to an understanding.
===Miss Triangle===
From before the show started up until "Untying the Knot", Mr. Triangle and Miss Triangle were married, meaning Miss Triangle was actually called "Mrs. Triangle" for all of this. They didn't interact very much, due to the fact Mr. Triangle eventually betrayed his boss and had to live away from her. In "There's Three Sides to Every Story", we see how they met and got married.
In "Eye, Roommate", we learn that Mr. Triangle does still love his wife, and misses her, which is probably to lead into the next episode, "Untying the Knot", where their ever stale and non-existent relationship is finally resolved, as they get a divorce.
Throughout Season 5, their relationship is put in the spotlight, with them spending time apart, and trying to make it work a couple times, until it reaches a breaking point in "Eye-ternal Voidshine of the Spotless Mind", which leads to Mr. Triangle being bedridden with depression, up until "Gregory Triangle" where he wakes up to find out everyone has been taken by The Ruler of Universes. Throughout everyone's battle with the Ruler, Mr. Triangle and Miss Triangle argue, but eventually Leslie sees that Mr. Triangle has been hurting and gives him advice to help him. Eventually leading to her jumping in front of a fatal blast meant for Mr. Triangle, ultimately killing her after the two share a loving goodbye to one another.