If you pause Minecraft in single player, anything moving stutters in the background of the pause window, and if you are moving, the whole game view stutters in the background. It the background of the pause window, instead of being still, like it should be.
I haven't tried this on multiplayer, but I doubt this will affect multiplayer, as the game continues in the background.

To replicate:
1. Move, or make sure something is moving in your view.
2. Pause