Bug in Yer Ear, Bug Up Yer Ass

Surely, the expression "bug in yer ear" didn't come from that scene in Wrath of Khan, where Ricardo Montalban put that blood sucking slug in Chekov's ear? Or did it? There's actually a small bit of cash hinging on this, because a friend of mine insists it does and I insist it doesn't. Anyone hear know?

And, while we're at it, where did the expression "bug up yer ass" come from?