This is some secrets and funny things I found in Bloodsteined, if you know some others, please do let me know :D

00:25 Breakable walls and hidden rooms
01:13 Ride on monsters
02:33 Playable forms
04:05 Hidden monster
05:25 Hidden chests
06:50 Hidden portions
07:51 O.D.'s chair treasures
08:46 Passing the trap
09:23 Fairy song
10:04 White shadow
10:40 Twin dragon boss bug
12:32 Full fairy song (enjoy!)