Magic: The Gathering

Patch

In 1999, Internet play arrived via a patch that allowed players to use TEN (the Total Entertainment Network.)

References

The data for all the cards in the game (type, name, description, etc.) is contained in a file called "master.csv" which is actually a .xls spreadsheet which can be easily read by Microsoft Excel. While it's fairly useless to edit it (saving changes leaves you with a corrupt game) it's interesting to note the amount of development-related jokes and references you can find in there. For instance, there's a "Terror from the Deep" card with an amusing description that refers obviously to Microprose's X-COM: Terror from the Deep, as well as other MPS games.

Information also contributed by Zovni