"A collection of insults 39" joke

Even a two button mouse gives him too many options.

Evidence for the theory of a missing link.

Failed the Turing test.

Fell out of the family tree.

Fifty-one cards short of a full deck.

Fighting the war with a starter pistol / water pistol / pop gun / cap gun.

Finds a flat by swapping tires.

Finds canonical humor collections amusing.

Finds Sesame Street / knock-knock jokes challenging.

Fired from McDonald's for having a short attention span.

Fired her retro-rockets a little late.

Flaky.

Flat out like a lizard drinking.

Flying/landing on one engine.

Focused like a 12 gauge shotgun.