A blue hat is found in the Kharazi Dungeon during the Legends' Quest. Trying to pick it up will turn it into Viyeldi, who will recite a poem about what is to come during the quest. After he completes his poem, he disappears and the hat returns in his place.
It was possible up to approximately 2005 to telegrab the hat. Dropping and picking it up caused the player to teleport back to the Viyeldi's cave (starting an animation sequence), even if the player was in the wilderness or the Duel Arena. Jagex fixed this problem approximately 2 weeks after it was discovered, resulting in the first un-telegrabbable item.