Are imported characters from the GBC version of the game allowed? I'm guessing no since it requires you to have the ability to transfer data from a GBC version to N64, but want to be sure.

I love how no one ever responded to this. I'm also looking for the answer to this question.

To anyone else who may come across this thread in the future, the answer is yes, they are legal.

They seem to have pretty big potential. I'm not sure about singles as I'm currently running doubles, but it seems that decently-leveled transfer characters don't suffer some of the same plights as your CPU partner/your player character suffer. For example, many times in a doubles run your partner doesn't "put away" a very easy overhead, but the chance that a transfer pak character does this with a decent power stat is significantly lower. Additionally, you can have transfer pak characters with a high power stat and, as a result, generally hit the ball harder than you should be able to in a standard tournament cups run with 'unstarred' characters (e.g. I can serve at 120 MPH with pak characters, and additionally 'starring' doesn't apply to pak characters, they just are what stats they are and always have the option to pick between tournament cups and star cups at the selection screen following when you select them as a character).

It's been so long since I messed about with them but I just don't even see a maxed out character from what I remember stand up to Baby Mario.

As much as I don't care about them being legal either due to that, I have to be honest if it was ever to be found that we could make the GBC characters the highest tier I'd be more leaning towards them being banned. The last thing a game like this needs would be another wall for accessibility to run it with the lack of recent activity as it is.

It probably will never matter as I've said, so maybe something that needs more extensive testing to make sure.