Mr Oborman is a brave but puny caveman living in a, well, cave...duh.
He loves to eat fish.

So, one day, when Fish from the Lake wanted to befriend him, he gladly accepted the offer.
He would be nice to Fish from the Lake, and slowly, gain his trust so that one day, when Fish from the Lake is weak, he would be able to devour him.

Muahaha! He laughed, as he thought of his ingenious plan.
Muahaha!!!