This is a blog entry about, you guessed it, arrows and repeaters. Or rather, how they interact. In this case, I'm talking less about just repeaters and more about repeater clocks:

1. An arrow shot into the repeater component of a repeater clock (or just any repeater that is going on and off) will be continuously and perpetually "shot". It will keep on hitting the ground and will keep on making the "arrow impact" noise.
I believe this is because on repeaters and off repeaters are two completely separate blocks, and when they are powered on or off, they change blocks. This change causes the arrow to temporarily fall, only to hit the new-state repeater when it appears.

2. An arrow shot into the repeater will never despawn.
The perpetual state of falling/motion causes this.

3. An arrow shot into the repeater will jiggle constantly.
An arrow, when shot, will jiggle a bit after finally hitting something solid. This the arrow in this case is constantly "hitting" something, it constantly jiggles.

4. An arrow shot into the repeater will eventually right itself to be perpendicular to the repeater. This takes about a couple seconds to do.
I think this is because arrows tend to right themselves when falling. For example, if you have an arrow shot into a block, and you break the block it was being shot into, the arrow rights itself to be perpendicular to the ground. Since the arrow in this case is perpetually falling, it's perpetually righting itself.

The reason why I made this was because I thought it was interesting, and also because you can annoy the heck out of your friends with the constant "arrow impact" noise and the fact that the arrow never despawns. Hehe.