Sonic Tweet is a digital application created by Sega of Japan as part of Sonic's 20th anniversary celebration. The app is accessed though the popular social networking site, Twitter. The application comes off as a game where the player must help Sonic defeat Dr. Eggman. The game, which requires the player to follow @SONIC_TWEET_JP and authorize it to be able to read the player's tweets, is a free mini-game that involves the player to tweet ”Sonic ★ Tweet”‘ as part of the Twitter message. Certain words from the message will make Sonic use a "Dash" to attack Eggman. Defeating Eggman will reward the player with 1 of 500 cards that can be collected or traded in for additional dash attacks. The cards are comprised with artwork or sprites from a group of 35 different Sonic the Hedgehog series games. The whole application is in Japanese.  The game ended on the 31 December 2011.
Sonic Tweet was launched by SEGA of Japan on 5 July 2011. By 18 July, the game had crashed do to an overwhelming amount of participants. A message in Japanese was left in place of the game which stated:
"We have had to stop the server as it is so busy.
Currently, we are investigating the failure and progressing toward recovery.
To everyone we are very sorry, thank you for waiting."
The game returned on 9 August 2011. To reward returning users, every account automatically received the Sonic card from Sonic the Hedgehog (1991). The game has some slight changes from how it was at launch. For example, Sonic and Dr. Eggman used to pass by signs advertising Sonic Channel, Sonic Colors, Sonic Generations and Sonic's 20th Anniversary. When the user clicked on the signs they would be taken to the matching website. However, when the return of the game, these signs had been removed for unknown reasons. The signs returned on 9 September, exactly one month after the game itself came back online. Sonic Tweet ended on 31 December 2011. Currently, the sprite animations have been replaced with Sonic chasing Eggman on foot and large text reading "Thank you for playing" is on the left side. Many of the features have been removed from the site leaving only the pages that show results in collection, point total and card total.
Sonic Tweet is nothing more than a free app for Twitter. SOJ is calling it a “Game-included Twitter Client”
The objective of the game (or app) is to collect 500 cards of characters from Sonic’s history.
To play, the player must tweet something using the app, and try to chain combos.
The tweet will be separated into single words, one of them will be randomly selected and assigned points. Apparently words like 20th or Sonic will receive more points. Then, the app will connect that word with words from other users and generate a combo. The higher the score, the more powerful Sonic’s attack will become.
Tweeting short sentences or tweeting the same sentence many times won’t be made into combos.
By attacking Eggman and making his HP go to 0, the player will receive a card.
To dash and attack Eggman the player will have to wait some time, but this can be bypassed by using the cards that are earned.
By defeating Eggman the player will receive exp points that will be used to achieve higher levels. The maximum attainable level is 10.
It will be possible to exchange cards with other twitter users, however to do this both users will have to be using this app and be followers of each other. Card trading is limited to 3 times per day, up to 5 cards per time.
There are three types of rankings, and going up to the third place will earn extra cards.
Different sprites from the original Sonic games are used in this game.
The Metal Sonic sprite on its Sonic the Hedgehog CD card was edited to feature its characteristic red eyes; in the original game, Metal Sonic only appeared with grey eyes except during the Stardust Speedway segment of the ending animation.
The first two 8-bit titles have background scenes recreated using sprites from the original Master System releases, even though Japan did not receive these games until 2008 via the WiiVirtual Console. In contrast, the Sonic Triple Trouble and Sonic Blast cards use a similar "console" resolution but lift their visuals directly from the Game Gear titles. Sonic Chaos is different in that it appears to use graphics taken from both its Master System and Game Gear counterparts.
Sonic the Werehog is the only different transformation of Sonic to have a card. Other transformations like Darkspine Sonic and Excalibur Sonic don't have cards. Super transformations (with the exception of Super Sonic) do not have cards.