Mickey Mouse & Donkey Kong Circus
Released rispectively:February 28, 1984; September 6, 1984
The Mickey Mouse Panorama screen Game & Watch and the Donkey Kong Circus Game & Watch were produced simultaneously and are in fact identical in terms of gameplay:
In Mickey Mouse the player controls the titular character balancing on a ball, juggling batons while avoiding flaming torches, and Donald Duck is on the left watching. Note that this game is not related to the New Wide Screen Mickey Mouse Game & Watch, instead a clone of Egg.
In Donkey Kong Circus the player controls Donkey Kong balancing on a barrel, juggling pineapples while avoiding Fireballs, and Mario is on the left watching. Also the background features platforms from the Donkey Kong game and oil barrels, that are where the Fireballs come from, like in the original game. This game is also notable for being supposedly a prequel to Donkey Kong, since the ape was originally Mario's pet in that game's backstory.
Notably, the example image on the back of the games' boxes even shows the exact same point in gameplay in both games. Additionally the two game's codes were swapped during production, as Mickey Mouse is DC-95 (that likely stands for "Donkey Kong Circus"), while Donkey Kong Circus is MK-96 (that likely stands for "Mickey Mouse").
Both games were developed by Nintendo, with Mickey Mouse being officially licensed by Disney.