In both versions, the entire Ork race are a Take That! at football hooligans even though fans tend to think of Orks as really funny but its kind of obvious its a take that when you realize they are to bricks what dumb as a brick is to normal people.
Among 40K's many planets with such names as Armageddon, Murder, Fenris, and Baal, one stands out as being differently horrible.
Birmingham is also known as the Black Planet, as it receives almost no visible light from its system's sun. As a result, the planet receives few visitors, and its inhabitants have become linguistically and culturally isolated. Its technology is primitive compared to the rest of the Imperium, as the musket is still in use among the natives.
WoTC released a few animated shorts before the release of 4th Edition Dungeons & Dragons, they focused on very specific monsters and races in terms of how 4th Edition would affect them. One of the shorts was about the red dragon and contained a very amusing reference to the "Edition Wars" in which traditionally whiny fanboys ranted about the suckiness and evil of 4th Edition. Said reference showed a forum being trolled by an actual troll that was promptly buried under a large pile of dragon excrement by the red dragon as it flew overhead.
From a supplement to White Wolf's Mage: The Ascension: "This same century also sees the birth of many of the modern 'gypsy' stereotypes, which... lead to the fanciful romanticization of 'True Romany' as singing, dancing, scarf-wearing vagabonds. This stereotyping is perpetuated throughout the 20th century through works of popular fiction, cheap horror movies, 'medieval' or 'Renaissance' re-enactment societies, and badly researched role-playing game supplements." The same company had earlier released World of Darkness: Gypsies, a supplement playing on exactly those stereotypes.
After the Secret Service raid on their premises was deemed to have been unlawful, Steve Jackson Games printed a card for their Illuminati: New World Order CCG depicting a Secret Service agent wearing the insignia of the Nazi SS.
A justification for the raid given was that the book whose manuscript they seized, GURPSCyberpunk, was a handbook on computer crime, especially hacking. The result? They made Hacker shortly afterward, a board/card game focusing on computer hacking.
Another, less malicious, Steve Jackson Games example, Car Wars featured an America that was mildly post-apocalyptic, having survived a limited nuclear engagement with Communists. The worst hit spot in Central United States? Lake Geneva, Wisconsin, where main rival game designer TSR games had their headquarters.
The ShadowrunSourcebookRunner Havens has the following gem during a discussion of Hong Kong pirates:
The bizarre Egg of Coot, a ruler in the Dungeons & Dragons Blackmoor setting, was a jab at Gregg Scott, an individual who'd previously given Dave Arneson some flak.
Palladium Books include a description of an alignment system which includes a statement against neutral alignments, a feature of the Dungeons and Dragons based games. One sentence reads: No neutrals is one of the very few definitive, unbending rules of the game.
The welcome page to Nobilis third edition refers to Guardians of Order having distributed the second edition until "they decided to stop sending out money and books and stuff and just lurk like a serpent, coiled around the dark heart of the world". Given what Guardians of Order were up to at the end, Dr Moran was probably due a shot or two.
There is some suspicion circulating that the ''Arbiter'' Battlemech from BattleTech, released as part of a technical readout in 2010, is a jab at Warhammer 40,000. It features several stereotypical Warhammer details, particularly those of the iconic Space Marines, including Shoulders of Doom, a gauntlet-shaped hand resembling a Power Fist, Spikes of Villainy, a huge gunin place of its lower right arm, and a vaguely Gothic Punk appearance. It also happens to be a weak, slow, fragile, poorly armed lightweight Industrialmech (that is, a work-grade robot) that is to a proper Battlemech what a forklift is to a tank, explicitly designed In-Universe to look more showy and threatening than it actually was, and bought precisely for its looks rather than its substance. Described as cheap, bottom of the barrel, and only good in large numbers, it's hard to not see some broad swipes taken at 40K.