Any number of things in El Goonish Shive, but especially Jeremy. Justified in that most of the characters are used to Tedd's bizarre experiments by now.
It's generally justified as the public generally being a little dumb every now and then, as well as the government being very good as upholding The Masquerade. When the new guy in charge stops trying to hide things, it gets more... complicated. Currently, the public seems to acknowledge a sudden superhero, monster attacks, and magic from a range of interesting news to complete awe.
Raven has a cat exactly like Jeremy, and is confused when Grace says it's "just a cat".
Inverted later on. After blowing up a spider vampire, the cast decide that they need to leave the scene, before people come to investigate the explosion. Reality Ensues during a quick montage showing various people who assume it's just some idiots setting off fireworks.
In Griefer Belt, Addie is so used to Lars's antics that even when she sees an ex-coworker walk back into the thrift shop after Lars amputated his arm, her reaction is to yell at him to get out since he's making a mess that she'll have to clean up.
Inversely, "Two Strange Girls" (Zimmy's introduction) sees Kat being offended that her anti-gravity device is getting more attention than the real purpose of her research: to see how protein crystals grow in zero-g.
Then again, it's the Court. One of four Houses is composed entirely of magical creatures — in at least one class all girls have pointed ears and wear Facial Markings on account of being fairies emigrated to humanity, and tend to act accordingly. They also got Ridiculously Human Robots milling around and grass in a park is mowed by talking laser cows. The previous generation had a student moving around via drawing huge glowing portals in the air. A talking shapeshifting plush wolf sometimes still get to surprise people, but Zimmy's face isn't the strangest thing they saw — or not for very long, at any rate.
And it's actually a visual metaphor, like how The Simpsons have yellow skin, or the hair colors in anime like Lucky Star, or even [[Homestuck]]'s Mom Lalonde not being drawn with eyes and a nose.
In Misfile, Rumi and Vash's angel ears. They are long and pointy, but no one comments on them. It is implied to be a sort of passive ability in the Ask Ash column, but is otherwise unaddressed.
Well, Logan instantly recognizes them as angels. Ash freaks out at first, but Rumisiel isn't too worried about it, saying that there are rare people who can tell angels apart from normal humans.
In Killroy And Tina, nobody except Tina pays much attention to the fact that Killroy is solid blue.
In Agents of the Realm, people seem strangely oblivious to bleeds rampaging around places such as the city museum or the Main Street, and Adele is unusually chill with the realization that her teacher is trying to kill her.
In The Inexplicable Adventures of Bob!, Bob was greatly concerned about Molly the furry pink monster's safety when she was first introduced to the strip—and indeed, newcomers do occasionally have a Herman Munster-like reaction to her—but for the most part, the neighbors seem oblivious to her. General concensus around town is that she is deformed, but nice.
Ms. Hatbrim: Heywood, she has claws, fangs, and a tail! Heywood: Well we all try not to stare...
The Order of the Stick when the sylph Celia is on a date with Roy in Azure City, gossamer wings and all, no one seems to take notice. Even when they are making out while flying in the air over the city. Then again, that was a holiday in a highly magical setting.
When Elan and Tarquin get to discussing Tarquin's evil plans, and ultimately dissolve into a sword fight, the Empress of Blood is sitting right above them on her throne during the whole thing (including Tarquin openly stating that he's manipulating the Empress as a pawn to be disposed of at a later date), and there's no indication she even noticed. Possibly justified by the fact that she's a gluttonous moron who doesn't care about anything but food.
Venus Envy: To quote Larson, "Okay, I can understand that they do things a little bit differently here on the East Coast ... but am I the only one who realises that the teacher is a chicken?"
In Mountain Time, nobody seems to notice that Otto is a four-armed triangle with an Eye on a Stalk. Most of the people in the comic seem pretty used to the idea of talking to ninja onions, so perhaps they've been primed.
In The Adventures of Dr. McNinja, the citizens of Cumberland are apparently fairly used to the eponymous Doctor's antics. For example, their primary reaction to a Zombie Apocalypse is annoyance that the mayor isn't doing more to protect them. Meanwhile, a Captain Ersatz of The Incredible Hulk runs a local convenience store, and nobody thinks twice about a gorilla walking into a pet store to buy a kitten.
In Our Little Adventure, the sun travels across the sky and explodes when the day is through, beginning the night which darkens the land in seconds. The moon does the same thing at the end of every night.
Stubble Trouble features a world where half the population consists of anthropomorphic animals, superheroes and supervillains regularly fight without much public or media attention, a long-dead president is resurrected as a Frankenstein/Hulk, dinosaurs can be seen at a zoo or while camping, magic raises no eyebrows, some people can live while being decapitated, a giant robot rampaging through a city is deemed "cool," and furries who have shaved their fur off generally aren't noticed.
In Homestuck, Jane Crocker is perfectly used to and exasperated with an omnipotent cat dicking around with her life.
Oh. Its just that GOD CAT again.
also nobody bats an eyelash at a game that allows you friends to remodel your house over the Internet. And there is very little surprise over the fact that it also launches meteors at your house and then teleports it to Another Dimension.
Dave initially mistakes the fiery apocalypse for a heat wave. To be fair, Houston weather can be like that...
Used deliberately by... someone in Power Nap by way of surprise 3D ads for explosion-filled action movies to disguise the actual attacks of... something that might have something to do with the fact that no one sleeps or dreams.
In Moon Crest 24 being teleported in a gust of light from a cemetery to her dorm room doesn't seem to faze Lucy in the slightest. Averted later on when she discusses it with Rachel and Dory.
Krosp I, Emperor of All Cats from Girl Genius. He is a talking cat created by a Mad Scientist; however, since Mad Scientists are rather common in the setting nobody baits and eye: They tried to teach him how to dance when traveling with a circus, as talking was not enough for an act; and was explicitly told to be uninteresting to the citizens of Mechanisburg, a town run by a family of Mad Scientists.
Erfworld begins when everyday gamer geek Parson A. Gotti swears to his tabletop buddies that he wishes he could vanish into one of his strategy games... and vanishes, having been magically summoned by the residents of an RPG-Mechanics Verse. The other gamers are more bemused than upset.
You know... Over the years, Parson's had a lot of big ideas. But this is the first one I've ever seen him follow through on.