There arent a lot of Homebrew games for the N64 but heres one that should give you foood for though:

Christopher Bonhage made a Flappy Bird for Nintendo 64 about eight months ago. If you like this very well hyped game, get out your Nintendo 64 now. The ROM file has been tested to work on real Nintendo 64 hardware using a EverDrive-64. It should also work with 64drive by retroactive.
The game is open source and released under a BSD license.

via https://pdroms.de/nintendo64/flappy-bird-n64-game