Here is a video of the Phantom Grand Slam, and here is the Phantom Grand Slam enGIF’d:
Base-rounding footage truncated for your loading pleasure.
If this is the first you are seeing of this grand salami, then I envy you. If that is not enough to sate you intellectual desires, watch the full clip (above linked) and that should both explain this oddity and remove a thin sheening of fun and mystery from the GIF.
After the jump, enjoy a fast-motion, more accurate rendering of the Phantom Grand Slam: