This fully-encapsulated OLED display inside of a run-of-the-mill-looking 2x2 sloped Lego brick, powered by a standard 9V Lego battery brick, is remarkable.

Created by James Brown using a slightly modified STM32F030F4P6 Cortex M0 processor, with 16K of flash memory and 4K of RAM, paired with a 0.42" QT1306P82 OLED panel. The final brick form itself is achieved through a combination of 3D printing and what appears to be a polyurethane casting technique (using Lego molds, no less) popularized by Keymacs.