Cat horns = something illusional?

Atavistic cats' horns are as rare as hens' teeth.

Don't get me started on rocking horses.

Unicorns or chicken fingers...

You are correct. Origin possibly in a children's game called "Horns":

Similar to "Simon says." All seated, forefingers placed
on knees or table. Leader says, "All horns up," "Cat's
horns up," "Cow's horns up," etc. If animal with horns
is named players must raise fingers, otherwise disobey. All fail-
ing drop out until the game is through. Since cats are not horned animals, those who raise fingers when "Cat's horns up" is called must drop out.

Another example of such a phrase is "hen's teeth". E.g. something very rare or nonexistent is "as common as hen's teeth".

How spice are the unicorn fingers? Sounds delicious! Thanks for making my mouth water and my belly grumble with hunger.

Thank you all.

Could it be a typo? "Everything but Car Horns"?

Well, bugger me.

Cat horns.

ori will be scratching his head