Gave it a Let's Play, unfortunately I gave up chasing after the mice since I swear I found them all expecting an achievement but either missed a mouse or missed whatever I should've done next. (Commentary will also have suggestions I already gave in the comments)
I just checked the locations of the princess teehes and grabbed them all. The achievement was given to me and I believe I know which one you missed! Also, the intro can be be skipped if you press "Enter" on keyboard and mouse or "Start" on controller. It used to show up during the intro, but I didn't like how it looked so I removed it before release. This will be addressed and changed in the update coming out this upcoming week along with several bugs and other things players have pointed out.
-Bradley