The amazing suckers on octopus arms aren't just for sucking. They also are used to smell and taste. To deal with all that sensory input, the vast majority of an octopus's brain cells are in its eight arms!
"It's more efficient to put the nervous cells in the arm," neurobiologist Binyamin Hochner, of the Hebrew University of Jerusalem, told KQED's Deep Look. "The arm is a brain of its own."