I’ve been thinking about this for the longest time. I havvvve to say more than one!:
When Finn kisses the Ice King’s cheek in Thank You, an acknowledgement that people/beings can coexist, and that at their core, people are good.
"We could learn a thing or two about those sandwiches."
When Jake crowns Cookies as a princess in Princess Cookies, affirming that it is alright to be anything or any gender you want to be/that feels right to you.
and in Lady and Peebles when PB fuqs up Ricardio and clarifies that she is not a mindless thing that can be wooed by an ego and fake intelligence.
gd I love this show so much.