What was the time a pet showed some serious signs of intelligence?

I'll start.

My then gf and I had a chihuahua that just happened to be the most tiny and most diva and most clever little dog I've ever met. Tiny, incredibly cute, extreme ego and confidence, a terrible piercing bark and had some wild mood swings on top. He'd go from cuddly to nuclear warfare in a second of something displeased him. He was the eldest and the leader of his little pack and he kept all of them wrapped right around his paw running a little dogmatic terror state. But he took his responsibilities seriously and was always up in front if there was a threat to them. Be it an angry German shepherd or a double parked electric scooter. Nobody messed with his pack - except for him, obviously.

Our little beast was very well aware of his cuteness, and his craving for adoration knew no end. He'd be walking down the street next to me, obviously refusing to yield for anyone, and as we pass some café tables, he'd throw himself flat on the ground, legs pointing in all directions. We called it that he did a doormat. The intent was to throw us under the bus as his keepers so that he'd maximize the aahs and oohs and attention went compliments from the people sitting in the café.

But this is just the backstory. He was vain, and we knew he was clever, but also of this is still learned behaviour with a previously verified outcome.

No, what really set it apart was that one time we were at home, the entire couch occupied by humans, dogs, and generally not him in particular. He was strutting around, being grumpy that others had taken his rightful seat, and nobody would disappear into nothingness for his approval. Not an uncommon thing, but he has plenty of other comfy spaces to be, communal and his very own. We know if we lift him up now, he'll try force some other dog down just because he wants space for himself, and we weren't having it. The other dogs were there first today and it's their right as much, so tough luck bud.

After some time, I notice him staring into the lights off bedroom. He looks at me, turns back to the bedroom and just keeps staring at it. I tell my gf that he is staring into the void and it seems to be staring back at him. We watch him as he keeps staring at nothing.

By now he is an old dog and has already shown signs of deterioration. I ask him what's up and he shows some signs of anxiety, tail down, tapping feet, mild whimper. I call for him, there's nothing there, come to daddy. No response. We figure he's lost it now, the creeping senility we've suspected is real.

So I keep talking to him, calming him, approach to turn on the lights and show him around that there is nothing there. He stands eagerly waiting, full focus on me as I come closer. Then - tail high, he runs as fast his tiny legs can carry his body, to the seat where I was sitting, barking at my gf to be picked up into the couch.

And it dawns on me. It was all a ruse! He came up with the clever plan to lure me away from his desired spot. If he acts anxious I'll get worried and get up, freeing up a vacancy on the couch, and then it's a fair race who gets it first. His smug posture standing in my seat was what gave it away. He was not anxious at all, he was not afraid, that I'm not anthropomorphizing but that he knew exactly what he was doing.

A multi step sequential plan with a clear goal in mind that he came up with from no be prior training. If that is not intelligence, I don't know what is.