This feature kicked so much fucking ass. You just needed one copy of a game, and 2-8 players could play multi-player for free.

I am still amazed how little lag it had having 7 other people join in on one person owning Mario Kart.

>Mario Party DS was also peak
>NSMB Mario vs Luigi mode is severely underrated

If you know then you know. But if not? You can't understand how fun it was to essentially have portable couch co-op with random people.