Here's two Pop Art images from the second half of the last century:
The one on the left is fake Pop Art by Roy Lichtenstein; the one on the right is the genuine article by Jack Kirby. Here's another pair, with a more action oriented theme:
Did you spot the fake? This time, the Kirby is on the left. The difference in quality between the artist and the bored doodler leaps off the page/screen.
The Kirby has vim, movement, and a degree of grit; the imposter's work is static, clinical (and cynical), and devoid of any real connection to its subject. The linework is also clearly much less adept and the coldness serves to point up the irony that this is the purely commercial effort, rather than the professional work-for-hire that Kirby produced for a cheque but nonetheless from his soul.
Indeed, Lichenstein did claim his work was ironic, even when he was simply stealing someone else's work. And to be fair there is an irony in that all of his most famous work is ripped off from real artists who he simply copied badly. This goes well beyond the simple imitation of style, genre, or atmosphere as in the above examples, but even dialogue in his pictures. For example:
In this case, the original at the bottom is by Irv Novick. If you can think of a print by our friend Roy, the chances are almost 100% that someone else did the work and he just took the credit.
"Pop" is short for "popular" of course, and the huge popularity of Kirby's work totally overshadows the niche appeal of Lichtenstein for an effete elite of buyers who's understanding of art is limited to the bits and pieces they see hanging in a few galleries when they're not shoving heaps of cocaine up various orifices. Kirby (and Novick and the may other artists ripped of by hacks like Lichtenstein) produced work that was seen, and sought out by, millions of people every month for decades, whereas Lichtenstein is hardly known outside of a few posters that get flogged in gift shops or "insta-style" picks from Ikea. The few bits he did which were original are hardly known at all, and for good reason.
Like that other artistic parasite, Warhol, Lichtenstein postured as a sort of frontiersman, exploring paradigms too "out there" for the mainstream, while in reality they were completely dependant on the mainstream of the art world for their living, and in particular on its almost complete ignorance of art and the work of artists. A thin veneer of "irony" and "decontexualization" and all the ethical worries vanish, further shoo'd on their way by the sound of rustling banknotes.
Never in his wildest dreams could someone so devoid of original thought as Lichtenstien have come up with this:
Let alone this:
So, if in doubt about a piece of Pop Art, the simple advice is to look for the signature - if it says "Roy Lichenstein", it's a fake.