While in theory it might seem great to have a symphony of cats running together, all of the shots are not staged. Although Hitchcock put up barricades to trap cats, they turned out to be less effective. He told Truffaut that:
“We put flat panels around the bottom of the stairs. Each owner came forward and put their cat in the cage and then we were ready to shoot. The cameraman turned on his engine and the prop fired. All the cats jumped right over the barrier; not a single one went up the stairs They were all over the studio and for the next few hours all you could hear were the owners walking around saying, “Puss, pussy, pussy.” … Finally, we gathered all of them together again and this time we put a net so they couldn’t run away. Everything is ready. Camera. Bang! This time only three cats ran up the stairs. All the rest turned around and desperately clung to the net. So I gave up.”
The thought of a hundred cats running around on set can be hilarious, but it’s also understandably a big hurdle. Given the circumstances, it’s no surprise that Hitchcock chose to remove photos taken with cats – even if the end result will be a stunning display of ingenious editing. And while viewers may have missed out on a few laughs, the story itself is certainly funny enough to make up for it.
https://www.slashfilm.com/998441/alfred-hitchcock-learned-the-hard-way-that-directing-cats-wasnt-one-of-his-talents/ Alfred Hitchcock learned the hard way that directing cats is not one of his talents