This feature isn’t exclusive to the Leonoardo, as [Michael] explains in a build he sent in – the lowly Arduino Uno can also serve as a USB HID keyboard with just a firmware update.

But despite its cute size, it comes packed with almost the same features as your regular Uno board ... or produced by the ...

[Damian] used the lowly ATmega16u2 to generate the video timing. The 16u2 is normally used as the Arduino Uno’s USB interface. The only external hardware needed is a single 120 ohm resistor.