That was a neato entry. The rhythmic, bouncy animations are great, the graphics are really neat and the concept itself - ambitious. And you get some extra points for puns... and undertale (if Toby Fox doesn't sue you :p )
Brace for criticism: the score counter simply displayed 99999 the whole time, the game just kept going, characters and score counter bouncing to the song that was already over. The biggest problem though is... the input of "every character" being ridiculously hard. I'm probably not the best around at rhythm games, but I really struggled to catch even a fraction of the notes. It simply felt overwhealming. Maybe reducing the number of possible inputs would help with that, or alternitively tone down the number of inputs per second. Still, you made it and solo - with good music and good graphics - you deserve a pat on the back :)