I was just looking through some old programs on my computer, and I came across Warp Pipe. I believe it was a third-party app that allowed internet play of Mario Kart: Double Dash. That port on the GameCube could be used to connect two systems locally, and play up to 8 players in a race. I’m not sue what other uses it had. This app somehow allowed it to work online! I only had a brief time with it and don’t remember much other than it might have been a choppy experience, but I did just run across that file and it brought back the memory, along with your post!