Theory: Mario Land is in both Party 2 and Land 2

Abstract
Mario Party 2 tells a story that is the precursor to Super Mario Land 2: Six Golden Coins, providing an origin to the setting of Mario Land.

Arguments

 * Argument 1: The iconography of both Mario Lands is aimed towards a castle.


 * Argument 2: In Mario Party 2, the name of Mario Land does not change depending on whether one plays the solo mode as a character other than Mario.


 * Argument 3: The actions of Wario between both games line up exactly. In Mario Party 2, he attempts to have the land named in his likeness, which sparks the events of the story. Wario, knowing his personality, would likely take matters into his own hands and steal the castle from Mario after not winning in Mario Party 2. This is exactly what happens in Super Mario Land 2.


 * Argument 4: The number six plays a major role in both games. Mario Party 2 has six playable characters and six boards. Super Mario Land 2 has six golden coins that seal/unseal the castle doors.


 * Argument 5: There is overlap in some of the location themes, such as in the horror-themed and space-themed boards and worlds.