First time I was aware of Mr. P I was visiting my older brother who was in a prog-rock/jazz fusion band. This would be around 1979. He put Jaco's debut record on his deck and out came Jaco at what seemed a hundred miles an hour! I kept asking "are you sure he's playing a bass?"
I discovered him again years later in my late teens when I started playing fretless. His playing can still cause shock & awe to the un-initiated, haha.