One of the ways that Krypto tries to wake up Superman is by shoving his ass in his face.
The scene where Krypto tries making small talk with a regular dog and pretends to be a normal dog himself.
Krypto: What is new with you, fellow normal dog? Normal Dog:(Awkwardly) …I bit the FedEx Guy the other day. Krypto:(Suddenly serious) Who was he working for? General Zod? The Legion of Doom? Normal Dog: …FedEx. Krypto: Of course! The Federation of Exes! Not to be trusted! (Beat) Normal Dog:(Turning away) …What is taking my owner so long?
The scene is already funny due to just how bad Krypto is at acting like a normal dog. But what makes it even funnier is the fact that his leash is tied to a nearby lamp post. To reiterate: Clark Kent, who likely had some errand to run, tied his super-powered dog, who's strong enough to easily win a tug-of-war against a freight train, to a lamp post to prevent him from wandering off.
Of course, at the end of the film, the first enemy the newly formed League of Super-Pets face happens to be this same dog, heavily mutated into a giant, glowing blue, Doctor Manhattan-esque dog.
Merton: (shocked) "What just happened?" (Serious) "No, seriously. What just happened? I can't see shit."
Then, once the pets break out of the burning shelter:
Merton: Update. I'm fast now, but I still can't see shit.
When Merton is finally able to see her friends after Krypto gives her glasses, she realizes that none of them were turtles like her.
Merton: That explains so much!
Krypto comments that his poop smells like sandalwood. After he regains his powers once the kryptonite he accidentally ingested is gone, Ace comments that he smells sandalwood.
Whiskers the cat is blown up by one of her own grenades, but she is then heard cheerfully saying she still has eight more lives.
Krypto's failed attempts at waking his owner up, which are all very dog-like such as jumping on top of him, pushing him with his paw or sitting on his face... then there's the final attempt, where Krypto simply grabs the leg of Superman's pajamas, lifts him up in the air and then drops him. This one works.
Superman: Aaand I'm up...okay, Krypto, we'll go for a walk...
One of Lulu's minions is shown defeating Cyborg by pulling a giant Duracell-style battery out of his back.
Later, Cyborg can't help free the Justice League because he's been put on airplane mode.
Every time that they switch from "animal speaking" to "what the humans hear", especially when it's in the middle of one of Lulu's monologues, as it is just uncontrollable guinea pig squeaks.
A lot of the news scrolls in the film are very humorous. During Lex’s imprisonment, it reads RICH PERSON ACTUALLY GOES TO JAIL. During the Guinea Pig rampage in front of the Daily Planet building, the ticket makes a number of comments like ANIMAL RIGHTS EXPERTS VERY CONFUSED and FASTEST MAN ALIVE NOW JUST MAN WHO’S ALIVE when the pigs trap Flash in concrete.
Lois calling the Justice League hotline, especially when one realizes it means someone set up a multiversal phone line:
Hotline Voicemail: If you’re calling from Earth-One, press one. If you’re calling from Earth-Two, press two. If you’re calling from Earth-Three…
Krypto's Imagine Spot where he throws Lois all the way from Superman's apartment all the way to the ocean - doubly funny, in a twisted way, is that by the time she lands in the ocean, it's now daytime, implying he threw her halfway around the world.
Krypto skimming through Dog-El's advice at the end of the film until he gets to what he needs to hear - one of the fragments we get is just Dog-El yelling "FIREWORKS SUCK!!!"
The scene where Lulu empowers a group of guinea pigs for her plan - there's something oddly funny about the fact where most of them get standard powers (like a pair gaining fire and ice powers, and one becoming half-gryphon), one of them becomes a hulking, anthropomorphic, human-sized Fabio lookalike.
One of the guinea pigs only gains the power to create rainbows, which obviously has no effect on Krypto.
The containment units that Lulu used to trap the Justice League and Lex Luthor is shaped just like a hamster habitat trail, complete with a wheel for Flash.
The fact that the Hall of Justice has a doggie door just for Krypto.
Krypto dealing with Clark going out with Lois by gorging on ice-cream while watching a baking show.
Ace banging his head on Wonder Woman's invisible jet. Twice.
On a related note, everyone pointing out that the jet is more transparent than invisible. Although it is invisible for the above gag.
In one particularly topical moment, Lex had his office made into a rocket, claiming that all billionaires have one. Batman confirms.
By the end of the movie, Lex is still on the containment unit while Lulu has been put inside a hot dog cart. Both say "I always knew I'd go down like this."
Just before, the imprisoned Lex asks if a cute animal is going to come to his aid. Whiskers proceeds to skip across screen and answer with a cheerful “Nope!”
While breaking Luthor out of prison, Lulu takes a moment to show him footage of the captured Justice League on a smart phone… before accidentally showing him images of the two photoshopped into pictures of pets and their owners. She claims that she was hacked.
The rest of the Justice League’s reactions to Superman and Krypto’s relationship:
Following the initial fight against Luthor, Superman proceeds to pet and baby talk at Krypto, who responds by licking his face. The League just stares at them awkwardly.
Batman: …I miss my parents.
Cyborg later recognizes Krypto as “the dog Supes makes out with.”
While captured, Superman squees over footage of Krypto getting along with the other animals. He awkwardly explains to the others that they would get it if they had pets:
Green Lantern explains that she thought she had found a pet raccoon on Oa. Turns out the raccoon thought they were dating.
Flash admits he once had a pet cheetah, but then it ate his landlord and destroyed his favorite couch.
Aquaman says that all the creatures of the deep are his friends… except for one eel, who knows what he did.
Krypto: Your owner's a hero too? Anubis: Anti-hero. It’s basically exactly like a regular hero, except way cooler. You make up your own rules, and then you break ’em. Also you can ignore most moral and ethical conventions because no one can stop you. Krypto: Yeah, that sounds a lot like a villain. Anubis: Anti-hero. Krypto: If he's anti a hero, then... isn't he a villain? Anubis: Admit he's an anti-hero or Black Adam will destroy you! Krypto: Very villain thing to do. Anubis: It's a fine line, not gonna lie.
Krypto ultimately gets rid of Anubis by betting that Black Adam can’t fly all the way to Pluto. Immediately, Anubis is dragging Adam by the cape into the sky.
