Boots learned to knock the cat-flap about 3 years ago. I have a bespoke wooden cover used to stop drafts in the winter, it fits over the cat-flap from the inside. He must have patted the flap extra hard one time, making it tap on the cover. He soon learned it got my attention and does at speed now, still makes me giggle every time I hear rat-a-tat-tat.
Rosie uses the back door catflap as a 'doorbell' then when you get there her nose is stuck through the catflap. When she was a puppy she could get her whole head through but she grew a bit!!
:LOL: That is one very chastened dog! Our Chassis - AKA Klepto Kitty and scourge of the neighbourhood - slaps the younger cats if they annoy her. Most things annoy her so they get a lot of cuffs round the ear. As she only likes one person in the world - Sam - I am sure I'd get a slap too if she could reach. She is also exceedingly vocal and says something which sounds all the world like 'eff off' if I remonstrate with her.
It's a great pity the right of free speech isn't based on the obligation to say something sensible.