Decription:

If you throw an ender pearl at a high part of a wall while sneaking, or if you sneak before the ender pearl hits, you can end up clinging to the part of the wall you hit, rather than falling to the ground.  This doesn't always work, but it is decently common.

Reproduce:

Throw an ender pearl at a totally vertical wall, and crouch before / just as it impacts.  You may need to try a few times, as it isn't totally consistent.

Observed Result:

You will "cling" to the wall / You will be in a state of sneaking like you were on a ledge, but on the edge of a wall.

Expected Result:

You would fall to the ground.

Possible Explanation:

When the ender pearl lands, it clips you slightly into the wall.  Normally, you would be pushed out, but since you are crouching, you aren't able to fall off of the block in the wall that you are "standing" on.