@JensJosefsson1 of Swedish web design agency WebMind sent me their new 404 page, it's cute and I love the funny bit at the end! After all, life is just a party!
Their previous error page depicted exactly what happens every time a 404 error is logged on any web server, anywhere in the world and it had a musical Easter Egg too. Google Translate told me it said "Our developers are looking aggressively to find your page. Meanwhile, as you can well console yourselves with some fine music."