There’s no limit to what you can do with an old Game Boy or Game Boy cartridge as Sebastian Staacks shows with this latest project. Staacks decided to tackle the problem of getting WiFi into a Game Boy cartridge. He found a solution via an ESP8266 chip and, using an EEPROM, stored a simple app that contained a keyboard the ability to browse Wikipedia.
You should try building one of your own if you can with the help of Staacks’s GitHub repository and the necessary hardware. And watch the video explaining it all above.