mc5 - ... so help me God.

My friend Doormatt invented the skip with steps (so you can get out of it easily).

I invented the barstool [but it turned out the blasted thing could be unreliable after a few drinks] so I give the patent away to avoid potential lawsuits.

Bob the dog

I invented the preposition fishing rod, but it never caught 'on'.

Boolbar

I invented a canvas house for mothers but I couldn't get a patent.

DrQu+xum

I invented a new spaceship but it never got off the ground.