April 03, 1992
In a scene Ted and Ryce, the two older children of the family, can be seen playing Super Mario Bros. 3 on the NES, and specifically World 5-3, with Ted notably playing with the Power Glove, and specifically the controller on it. Curiously they seem to be both playing at the same time, but the actual game doesn't feature two player simultaneous gameplay in regular levels (and only one player character is shown on the TV). Ted also says his sister to leave "that leaf" to him, referring to a Super Leaf, while she would get the next one. The second player do is able to replay a level already played by the first one, in case that player didn't beat it, but all items always return, so it makes no sense to leave one for the other player.
Additionally, sitting near the TV are the boxes of other NES games: Pin*Bot, Zelda II: The Adventure of Link, Donkey Kong Classics, Kung Fu, Ice Hockey and Golf, but these are considered just incidental references.
The creators of Beethoven held no right over Nintendo's Mario, but they only included a minor appearance of the game.