Cats in a flap

I'd bought a Microchip-enabled cat flap over the internet some time ago. Today we drilled a damn great hole in the door and fixed it, but not before grabbing each cat by the neck and forcibly registering their microchip by sticking their head through the cat flap (since they wouldn't do so voluntarily). They both fought furiously, a bit like Neo in The Matrix before the bug is released into his navel.

Unfortunately, both our cats are either a bit dim or very, very crafty. Neuroticat has used a flap before, at our previous place, but she pretends as though it's now somehow optional, and parks herself in front of the patio door in protest, miaowing plaintively, as in "Why are you torturing this old woman?" Why? Because I've seen you negotiate the cat equivalent of Stefka Kostadinova's world record in the high jump, girlfriend! "Old woman", my cheeks...

Chunky, the black and white bruiser, has also clearly used a cat flap in a previous life but has decided that as long as the house serfs wave pieces of cooked chicken on the other side of the flap, acting like a customer at the Kentucky Fried Chicken drive-in window has more benefits.

  "That's not what I ordered."