Along with the attitude/demeanour thing mentioned by Rhaedas, once you spend a bit of time around them they each have an obvious 'tell'.

• Morgue has long flowing fur unlike the rest.
• Skeeter is shaped like a seal (and is on a diet trying to fix that).
• Eddie and Gary are both lithe and sleek, but Gary is a solid 1/3rd smaller which becomes apparent when any other kitty is nearby. ANd his eyes are a dark orange while everyone else has yellow/green eyes.
• Batman is quite a bit larger than everyone else and his age is showing in his fur.

Even a bunch of tabbies can be confusing until you know their personality, and then it's easy to tell.

Funnily enough the video on the TV was of blue jays and chipmunks in the yard which they have a full view of from their big catio or the patio door in our bedroom any time of day. SIlly buggers.