I think this isn’t too difficult to prove for animals that dream. Emotions aren’t something only humans experience. There are limits to how intelligent certain animals can be (ants and spiders are a whole different class compared to squids and dolphins) but there’s also far more to animals than the simple behaviourisms they exhibit. Even basic animals can have a personality, no matter how crude that may be compared to the personality of a human.

It’s as hard to prove that a mollusk has a rich inner life as it is to prove you have. For all I know, you’re an LLM, and for all you know, I am. Even if we are both people, who says you’re not an “NPC” merely pretending to be an intelligent person?

Proving consciousness all comes down to “I think therefore I am”.