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Comic books from the major publishers DC and Marvel are prone to this in general due to Comic-Book Time and the desire to keep memorable stories as canon. For example, the New 52 has established that the Batman story The Killing Joke is still a part of Barbara Gordon's history happening some time in the past five years but the original story was written in the late 1980's. Batman the Animated series even invoked this as an intentional design decision featuring art deco architecture along side 1950's looking television alongside almost sci fi level tech such as virtual reality and bionic eyes.
The eponymous character of Léonard le Génie is an inventor living in the 14th century. However, he has electricity, modern tools and a Cool Car available, and his inventions include computers and robots, among others. Somewhat justified by him being a genius inventor, but still...
Lampshaded at least once; Léonard invents a photo camera and, on having put the film into an envelope, realizes there's nowhere to mail it to. "Do I have to invent everything myself?"
Hellblazer occasionally falls into this, the most Just for Fun/egregious example being issue 186's anvilicious portrayal of the Black War as a one-sided Nazi-style genocide, completed with a barbed-wire-fenced extermination camp in 1833 (30 years before the actual invention of barbed wire).
Astérix is a mixture of this and Purely Aesthetic Era. The albums set abroad in particular include lots of elements for which the countries in question are famous now: bullfighting and flamenco dancing in Hispania, anonymous bank vaults and fondue in Helvetia, rugby and afternoon tea in Britannia, etc. Likewise, the regional specialties from different parts of Gaul in Asterix and the Banquet are all based on modern French cuisine. On the other hand, a lot of the stuff is actually well researched and Uderzo, for instance, later was quite embarrassed about some unintentional anachronisms, such as the appearances of a fiddle and a wheelbarrow in two early stories.
Hob Gadling, a character from The Sandman, has been alive since the 13th century and now will not die unless he chooses to. In the 20th century, his girlfriend dresses up to visit a Ren Faire. He has several criticisms about the realism of the place (mostly that nothing is covered in shit the way it should be), and when he sees her in wench costume, she attempts to talk Ye Olde Butcherede Englishe to him. His response: "Thou lookst passing fair, milady. Save thou manglest the Queen's good English and thy tits are hanging out."
Delirium is this on legs. She turns up in ancient Greece wearing a fishnet vest and miniskirt.
The newspaper comic strip B.C. had lots of these. Despite supposedly taking place, um, in the years B.C. (specifically, in prehistoric times), there were often references to modern times, especially as the strip went on; at least one strip had a character refer to the United States. It turns out that the series actually takes place After the End, with mankind reduced to the same level of technology as was had in prehistoric times...
Plus, especially in later years when Johnny Hart became more religious, they celebrated Christmas and made other Christian references. Which is kind of the definition of anachronistic in a strip named B.C.note Though one of the major characters is named BC, and the strip could be named after him rather than the other way around. Later strips sometimes feature an Italian-esque character who lives across the sea named Anno Domini.
"The Wizard of Id" by the same creators is another case of this. It supposedly takes place in medieval times, but it has plenty of modern-day references.
Deliberately used in Alias to lampshade the Marvel's floating timeline. For example, a flashback to Peter Parker's teen years uses fashion and slang straight out of a 1960s Silver Age comic, despite the fact that it was actually set in the late 1980s.
Lampshaded again in All-New X-Men, another Bendis work. The original X-Men likely started off in the early 1990s or late 1980s thanks to Comic-Book Time, but still dress and act as though they came straight from the 1960s, when the original X-Men comics were published.
Scion took place on a world which combined medieval European fantasy trappings (kingdoms, castles, dragons, etc.) with sci-fi elements (holograms, bioengineering, computers, etc.).
One of the stories in Captain Marvel Adventures #95 (1949), History Goes Wild, has an invisible version of Earth in space with history different to Earth, long ago the twin worlds branched apart in space. The North Pole has just been discovered, people are using rocket ships to return from holiday in Antarctica, people with different eras' clothing style are together, and cats and dogs are extinct. Also, President George Washington is on holiday in Antarctica and Julius Caesar is attacking America. Captain Marvel shoves the world away to another star system.
Opal City from Starman was deliberately designed to have a retro Golden Age aesthetic, despite taking place in the 1990s. The series' protagonist, Jack Knight, ran an antique shop and was quite fond of using dated slang and clothing.