I was playing on Creative mode and decided to make a lava trap. When I was filling the pit of lava, I right-clicked a block of lava, and there was a weird effect. It sounded like stone breaking, and had lava-esque particles flying away from it, as if I had broken the lava. The lava remained, and I did the same thing for more than one block in multiple environments.

Steps to reproduce:
1. Open your inventory and select the Misc tab.
2. Select the Bucket of Lava and close your inventory.
3. Place a block of lava.
4. Not moving the mouse, click your "Place" key again, and the effect will occur.

This isn't exactly game breaking, just rather odd.