It's based on the tasmanian king crab and the larger claw for the mega is supposed to resemble a spinosaurus head
Idea for a Pokedex entry:
All the power From mega evolving went to the small left claw and caused it to grow larger than it's right claw. It's left claw can cut through solid steel like warm butter.
And yes the title was a SpongeBob joke
by Traditional_Dig_4920