even round knobs aren't safe. i had a pair that would work together: one jumping to turn the knob while the other stuck their paw under the door and pulled.
Doyoyoyoyoingggggg
Doyoyoyoyoyoyinnng
OK fine I'll open the door but this is the last time.
I just love how he knew that I was sleeping and found out how to make the loudest possible sound in my house, all while staring at me of course, without even having to raise his voice.