My god, this is too adorable.
Not A Creature Was Stirring...
Not A Creature Was Stirring... (except Squeaky Whiskerson and his Marvelous Musical Mice!)
It's kind of like a demoscene demo, except with ballerina mice and stuff.
This was made for Day 7 of the 2018 PICO-8 Advent Calendar project.
(Note: this HTML version may have audio sync issues; switching to a different tab while it's playing is not recommended! Download the executable version for more reliable results)