(hex:C2) is a glitch item in Pokémon Yellow. It is an unterminated name glitch item.When a 0x50 sub-tile is present early in the saved screen data, then outside of battle this glitch item will bring up Professor Oak's message that it isn't the time to use the item.
If used in battle with an early 0x50 sub-tile in the saved screen data (the only known way this is possible is through arbitrary code execution), it will function as a stat-stage raising item and its quantity will be decreased, but there will be no other effect (the game will state "Nothing happened!").
Without the proper screen data, using this glitch item may cause the game to freeze (if there is no 0x50 sub-tile in the screen data) or function like 4# ぅ#▶ 't4# (hex:7C).