Fun and potentially useful stuff lightningkatana / me / itscolby found while running this game for a day:

Start-Button Cat: If you click on the start button around this spot, your cursor will instantly land upon a cat and you can click it right away. There is a delay before you can actually click, so a way to consistently get this cat is just to double-click on it after clicking the play button. If you miss, just hit ESC and start over until you can line it up. Free cat.

Counter-Cats: There are two cats hidden behind this counter that you can actually click while the counter is covering them. No need to move the counter until you can see them. The exact location will depend on how you panned your camera, but if you pan all the way down from the start, they'll be approximately at these locations.

Cat-Panning: Panning the camera will often lose you time due to spending time panning, and it also makes it hard to be precise after the pan. For these reasons, you'll typically want to limit your pans to as little as possible. However, when you are forced to pan, instead of panning by clicking somewhere on the screen and then dragging, instead use a cat to click on and then drag. This will combine both actions (panning + clicking a cat) into one and save you time. You can further optimize this by doing line-ups with your pan-cat, ie dragging the cat 40% of the way up the screen in order to get the resulting pan screen to be at the exact location you want it to be at. It's theorized you could maybe do multiple cat-pans in order to group the cats more favourably and optimize your route.

Buffer Clicking: At the start of the game, there is a slight delay before you can click on a cat. If you right-click and then left-click, you can click on the cat slightly faster. Useful if used in conjuction with Start-Button Cat.

Zoomed Cursor Teleport: This only works if you have zoom set to 3x. The zoom-in animation is slightly slower than 2x zoom, but the zoom out animation is instant, and when you zoom out, your cursor will "teleport" to the same point on the screen as where it was while it was zoomed in. You can click on cats while the zoom-in animation is happening, and ideally you find a line-up where when you zoom-out, you can instantly click a cat wherever your cursor lands. When you zoom-out, your map will also pan up to the very top, meaning you can click cats + teleport cursor + pan up all in one action.

A video from lightningkatana of an example of how it works / could be used

Horizontal Aimlock: If you hold down left-click, your cursor locks onto the x-axis, allowing you to "draw" straight lines left and right with ease. This makes it very easy to quickly hit two or more cats that are horizontally adjacent to each other. It also makes it much easier to hit pairs of cats that might not look like you could draw a straight line to. Example shown. Normally 57>39 requires you to aim slightly up and to the left, but you can aimlock 57's head and easily touch 39's feet.

The route I used: