Idea that I stole borrowed from Steven Universe.
If you were to burrow your face into the tail you'd pop out of a small planet made of fur.
Air exists there, but it's kinda cold.
Stuff can be hidden inside of the dimension - that'd kinda explain the cartoon physics behind magically appearing items from behind the back :D
Now back to work.
Link
gummiroo
I wonder if he kept going into his own tail, would he totally disappear from the other universe?