No piano arrangements here, this is the real thing. Showtime, the Haunting Piano Refrain mix by Kevin Regamey (which was based on and made after the 8-bit version of Showtime by Malcolm Brown), from MSPA's Homestuck. This was done entirely by memory, from the sheet music Kevin wrote quite a while back.
There are a couple of small mistakes, both accidental and deliberate in here, but after trying to record this for hours it's the best I managed to come up with - and unless you've memorised the sheet music, it's highly unlikely that you will be able to pick them up. The recording on the Homestuck album is slightly different to the sheet music version, so don't try finding mistakes based off that.