An Argument is a gameplay "feature" of Tomodachi Collection and Tomodachi Life, the angry version of a conversation. It occurs when two Miis are together in the same apartment in Mii Apartments, facing each other while exchanging banter between one another, usually leading to one of the Miis showing negative reactions like throwing a temper-tantrum while the other Mii sulks in sorrow. One hint of a possible argument about to break out during such a conversation is if the listening Mii has an angry expression flicker on his/her face for half a second as the other Mii talks.
If both Miis display this temper-tantrum animation for large amounts of time, it will lead to an immediate fight (unless the maximum number of fights at one time has been reached), and attempting to either shift to another apartment or enter the apartment depicting the Miis arguing angrily will cause it to occur instantly. When the fight occurs, both Miis will shake angrily as a horror sting plays, followed by the caption "[Mii 1] had a fight with [Mii 2].". If a fight doesn't occur, it will drop a Mii's relationship by one or several levels (possibly enough to bring it from either the highest two stages of relationships to the lowest instantly), and if the number of maximum Fights are already present (three), the two Miis will simply stare at each other with their "sad" expressions while the "Fight Start" sound effect plays.
Sometimes, but not often, the two Miis will instead talk friendly with one another and show positive gestures, which raises the relationship level as opposed to lowering it. However this type of conversation is uncommon and is more likely to curve into an argument.
Arguments can only occur if the game is left idle at Mii Apartments and the player or the game itself changes the focus into the apartment of two Miis chatting, leading to their friendship/relationship status tanking, regardless of how long the argument lasted before the player interferes. They cannot occur if the player is in the overworld or at Mii Homes.