I had a bit of an odd (to me) experience yesterday - since OldBoyCat became diabetic, we use a petsitter when we're away who comes in to feed the cats and inject OldBoy. We've only used her one session so far - she came in over 3 days in early April.
So Petsitter came round yesterday to collect the house keys, and OldBoy just went nuts - chirrups, purrs, demands to be stroked, louder purrs, jumping on her lap and putting his face right up to hers. It was like he was greeting a long lost friend, rather than a woman who stuck a needle in him for a few days last April. So he clearly a) remembers her and b) adores her - and I don't know why, but I was really surprised that he had the brain/cognitive abilities for that. Have I been underestimating cats?