When performed, Jigglypuff inflates slowly to an extremely large size, enough to cover the entire length of Final Destination, pushing away opponents that make contact with it while inflating. Once at full size, it shouts "Jiggly!", dealing about 15% damage and extremely high knockback to any opponents nearby, which may result in a one-hit KO with the right conditions. After this, Jigglypuff quickly shrinks back to normal size, ending the move.
Jigglypuff using the move, on Temple. Notice it size.