A bunch of the Mega Modem stuff is designed around some on-line service that of course is long gone by now. But some of them actually feature some form of off-line mode as unlikely as it sounds.
1200bps modem noises
Mega Anser was a piece of home banking software. Of course, the service is not available anymore, but what many people don't know is that it still works without the modem (in part because it's one of the few things that doesn't work without a standard controller, it needs the Ten Key Pad).
If you try to use Mega Anser without a modem connected, it'll go into "practice mode" (練習用). In practice mode, Mega Anser will give you a few bank accounts with 1,000,000 yen each and you can do everything you would normally do with a real bank. You can also set up the password, change the modem settings, etc. Occasionally it'll even pretend that there was a connection error.
Sansan, SanSan, San San, whatever. サンサン
This game was used to connect to the Sansan service to let you play Go with other people on-line. Of course, the service is gone now, so people assume that it's unplayable anymore. What most people don't know is that it has a local multiplayer mode! (or something that can be used like one — no AI players, sorry).
Sansan will refuse to go anywhere without having initialized memory, so if this is the first time you're playing it you need to do this:
- Select the 4th option (メンテナンス — "maintenance")
- Select the 2nd option (メモリークリア — "memory clear")
- Select the 1st option (はい — "yes")
Once memory is working you can access local multiplayer as follows:
- Select the 2nd option (棋譜の研究 — "practice matches")
- Select the 4th option (電子碁盤 — "electronic Go")
Note that both players share the same controller (taking turns, of course).