Sometimes, you need to start off your week with a dose of happy news. For instance, this video from the American Museum of Natural History details two recent instances where scientists have observed a whale and several dolphins interacting in ways that are something we might classify as "play".
It's hard to talk about animal behavior without getting too anthropomorphizing, but think about it this way: In both instances, the whale and dolphins did not appear to be competing with other, they did not appear to be fighting, nor were they cooperating in a goal-oriented way. When scientists say "animals are playing" they don't necessarily mean "play" the way human children play, but they do mean behaviors that go beyond simple eat/sleep/defend/breed necessities. Play might be learning. Play might be about forming social bonds that help an individual later on. And however you interpret it, spotting examples of spontaneous, inter-species play in the wild is kind of a big deal.
And now, with those caveats out of the way, I'd like to highlight the top comment on YouTube, by one Bill Kiernan: "We both used to be land animals, isn't that crazy? clearly we need to hang out."