He has a talent for taking things that cats do and turning them into a funny situation. I'm sure most cat owners can identify which is why his vids are so popular. I don't think any of my cats do all the things that Simon's cat does, but of all the various cats that Ive had there will be one that I can say 'yes my cat does/did that'.
For example Charlie used to sleep on my head and why he always had to be locked in another room at night.
Zoe does the tissue box thing - if you leave a box of tissues out she pulls them all out. She also cant abide closed doors and will find a way to get out or go into destructo-cat mode.
Ziggy does lots of silly things - too many to mention - but he is guilty of loo roll unravelling.