Castle Infinity was the first commercially launched MMOG for children. It was launched by Starwave Corporation in 1996, and featured personalized avatars, an embedded message system and live chat in a 2D side scrolling game world. It survives as a freeware MMOG.
The game is full of interactions that force players to collaborate with each other in order to pass from one area to the next, by way of four-person vehicles and other game-like lobbying devices.
Castle Infinity was first released in 1996, making it the first fully released MMOG designed for children. It was originally designed by Russell Ginns, Gregg Foster, and Scott Wallin, with art direction and animation by Jonathan Maier and Andy Norman. It was developed and published by Paul Allen's early internet company Starwave.
Access to the game required a CD-Rom and also a subscription. This technology requirement, plus the nascent child online audience at the time, proved too limiting for wide distribution. At its peak, the service had approximately 4,000 registered players. Ownership passed to Disney when Starwave was acquired in 1997. Disney did not maintain development for the game, and access to the service became intermittent starting in 1998, and was shut down entirely by 2000.
In 2000, the game servers were rescued from a dumpster by Kevin Quitt, a C programmer who happened to be one of the game's players, and new development of the game began run by Castle Infinity, Inc. a non-profit organization. In 2005 there was fresh media coverage of the game by way of Slashdot and BoingBoing. In 2011 a new server was launched with the help of former players, including Spencer Jerome, Donald Butyen and Rachel Coleman. At present, Castle Infinity, LLC, manages the effort.
Castle Infinity takes place in a virtual world created by dinosaurs 65,000,000 years ago to escape from a comet approaching the earth. Unfortunately, monsters have infested the place. Fortunately, mammals have evolved to the point that they have invented the internet and can now access the Castle. Players are welcomed in by dinosaurs, who want mammals (kids) to help them save the Castle from the monsters. 
Castle Infinity is a 2D side-scrolling world, where players collect "grow caps" and "hats" to unlock new play areas. The game places a heavy emphasis on player interaction, and much of the game's map is constructed to encourage users to collaborate in order to proceed. Players complete challenges which require multiple players to participate together, such as piloting a submarine that requires four pilots to steer properly. There are many locations where, in order to access higher levels, at least 3 or 4 members are required to stand on the same spot for the lift to activate.
Much of the directing players between single and multi-player environments was a solution to the challenges of latency. The game was launched when a majority of home users had 9600 or 14.4k Modems. By siphoning players into individual areas, they could experiences expected side-scrolling action. Then, in 4-player or unlimited areas, the focus was on communication and exchanging items.
The game's "official language" is Esperanto. Many signs and audio clips feature warnings and comments in a pidgin version of that language.
- "Starwave and Blockbuster to offer new multiplayer Internet game; Castle Infinity poised for nationwide launch.". Business Wire. September 10, 1996.
- LewisCastle, Elizabeth (April 1, 1997). "Get in Here, Kid!". WIRED. Retrieved February 22, 2017.
- Haines, Thomas W. (November 7, 1996). "Starwave Wants To Take Kids To Castle Infinity -- Firm Breaks Into Online Games". The Seattle Times. Retrieved February 22, 2017.
- Baker, M. Sharon (November 10, 1996). "Starwave is game for the Net with new CD-ROM products". Puget Sound Business Journal. Retrieved February 22, 2017.
- Luechtefeld, Lori (February 13, 2009). "5 online initiatives we weren't ready for". imediaconnection.com. iMedia Connection. Retrieved February 22, 2017.
- Colker, David (December 24, 1996). "A Game Kids Could Play Into Infinity". Los Angeles Times. ISSN 0458-3035. Retrieved February 22, 2017.
- Castle Infinity Revival Project Website
- Castle Infinity website from Starwave era
- Castle Infinity website from user-owned era
- Excerpt from Attack of the Show featuring Castle Infinity
- Slashdot thread about the return of Castle Infinity