Robert Heinlein famously wrote that "man is the animal that laughs," and it was just one of the many things he was wrong about. Dogs, among other animals, appear to be able to laugh. It doesn't sound like human laughter (leading to nitpicking debates about if it counts as laughter), but it's a specific type of panting they do when they're playing that is scientifically distinguishable from regular old "I am overheated and designed weirdly" panting:
As much as we'd like to think so, they're not just doing it for our benefit, either. When recordings of dog laughter are played for other dogs, they pick up toys or exhibit other behaviors signaling that they have accepted the invitation for mutual wigglebutting. Conversely, when the sounds were played for stressed animals in shelters, they became quiet and calm.
This suggests that dog laughter serves much the same function as ours, at least as far as we can determine its function: to bond socially (which is why, instead of laughing when you're alone, you just breathe really hard out your nose) and to signal a lack of danger to your peers. Whereas we laugh because the overpaid manchild on the screen isn't really getting whacked in the balls, dogs laugh to let everyone know that the giant beast chasing them means them no harm and is, in fact, the food source. That means everyone in the audience of a Judd Apatow movie is no better than a drooling, butthole-sniffing dog, but we knew that already.
Top image: Krzysztof Hepner/Unsplash