I'm 99.9% sure it has to be 1 pet. I JUST did this one. I didn't keep exact numbers, unfortunately. But I was feeding all 4 pets cakes pretty much as often as humanly possible, and after I'd gone through what felt like surely more than 100, I dropped down to just feeding my main pet. Eventually it proc'd after that. Because I was going through SO MANY cakes before, I'm pretty sure I would have gotten it back then if multiple pets worked.
Here is the node, you who hate change and fear revolution. Keep these two squatting men apart; make them hate, fear, suspect each other. Here is the anlage of the thing you fear. This is the zygote. For here "I have lost my land" is changed; a cell is split and from its splitting grows the thing you hate—"We lost our land." The danger is here, for two men are not as lonely and perplexed as one. And from this first "we" there grows a still more dangerous thing: "I have a little food" plus "I have none." If from this problem the sum is "We have a little food," the thing is on its way, the movement has direction.