Software for the Alpenglow Industries Krampus board. https://www.alpenglowindustries.com/store/p23/krampus.html#/
Krampus has LED eyes and tongue and is based off an ATTiny4 processor.
To use this with Arduino, you'll need to install the ATTiny10 core from technoblogy: https://github.com/technoblogy/attiny10core
The eye LEDs are on PB0, the tongue LEDs are on PB1, and a mode switch is on PB2 which switches between flickering and glowing LEDs.
The .ino file is fully commented for how it all works, look there for more details.