I mentioned this in my first post on the ROTJ Wishlist Thread.

George made three films where two droids were meant to be characters we cared about and two where the torture of humans was suitably horrific (within the set audience parameters naturally) and in ROTJ he dropped in a comedy droid torture scene.

This carried over to the PT where the battledroids do little comedy skits in between killing people and where R2 laughs his socks of in ROTS at the prospect of his pal Threepio getting a forced lobotomy.