R2-D2 is so devoted to charity, he risked his own circuits to help out with it.
R2 did take some precautions, wrapping himself in a protective layer so that the water and ice didn't do too much damage to his circuits. Based on that sound R2 makes, I don't know if it protected him too well.
A Tusken Raider did the honors of dumping the bucket on R2, though in a dark turn, used what appears to be another astromech droid's head to do it. Hopefully, R2 left soon after this, because you know that Sand Person is going to be back later, and with greater numbers of ice buckets.
Though the video cuts off before R2 can nominate anyone, we're going to assume that Wall-E, Johnny Five, and Optimus Prime are up next. [Editor's note: he actually did nominate Anthony Daniels and Grant Imahara].