The inventory in the Flea battle is loaded with all items, and an equivalent number of items to the item index (1 Wood Sword, 189 Tonics, etc). The video demonstrates using item 0xF2.
The item itself has no effect, but it tries to play an animation. The data it grabs for the animation is actually part of RustTyranno's AI, which causes a black screen when processed.
There isn't anything that can really be done with this beyond crashing the game.