Warning: contains spoilers for Amazing Spider-Man #88.BEY!
While Stan Lee and Jack Kirby are the key creators of the Marvel Universe, they haven't entered the universe proper - until the events of Amazing Spider-Man #88.BEY. The partners created dozens of superheroes and shaped the modern world of comic books as readers know it today. But the pair is properly introduced via the latest Spider-Man adventure - and they're hardly heroic.
While the Marvel writers have made occasional cameos in the Marvel Universe before, the one perhaps best-remembered comes in Fantastic Four Annual #3. After the landmark wedding of Reed Richards and Susan Storm, Nick Fury turns away two guests who appear to crash the reception. While the reader can't see their faces, the party-crashers are heavily implied to be Stan Lee and Jack Kirby themselves (if the indignant "We'll show 'em, Jack! Let's get back to the bullpen and start writing the next ish!" was any indication). Their last names, unspoken in 1965, are finally written down in 2022.
Hobie Brown, otherwise known as the Hornet (formerly the Prowler), meets with his lawyer after his company, Fairgray, is bought by the Beyond Corporation. Ben Reilly - the current Spider-Man - already knows Beyond is a sinister operation, but Hobie does not, and wonders why his lawyers didn't tell him of the hostile takeover. His lawyer informs him that "...Goodman, Lieber & Kurtsberg represents Fairgray, not you, personally. The senior partners handled these deals. I'm really just your liaison." Lieber and Kurtsberg are, of course, the real names of Stan Lee and Jack Kirby, respectively.
In the past (and present, unfortunately), Jewish writers used pen names to hide their religion from the general public. For his part, Stan Lee admitted to changing his name because he used to see writing comic books as a temporary occupation (he wanted to be a "serious" writer). This easter egg unfortunately plays into a stereotype regarding Jews as money-hungry lawyers who throw their morals to the wayside in exchange for a paycheck. While that was almost certainly not the writer's intention, it does read as particularly tone-deaf, even as the Stan Lee name is forever placed on a pedestal within Marvel.
It's interesting for the company to partner Lee and Kirby in a law firm regardless of the Jewish connection. As an artist during the "Marvel Method" period, many fans consider Kirby as instrumental in creating characters as Lee himself. Regardless, Stan Lee and Jack Kirby are officially introduced into the Marvel canon - and they're indisputably the villains in this Spider-Man story.