In the original location of the Smile effect, it is possible to collect more than one due to a "switch definition" error.
You cannot get this from there when you have owned the Snow effect.
(The one in the debug room isn't affected, it only allows you to get it there once.)
When pinching yourself awake at Aitsuki's dark balcony, her sprite becomes normal instead of remaining dark.
When waking up while being in the Heartbeat Maze, its BGM will continue playing after you wake up.
This continues until you save your game again or open the music box.