Throughout the years, Magic: The Gathering has taken influence for cards and sets from any part of culture that even borderlines on the word fantasy. Pretty much every biome has been represented at some time, along with influence coming from everywhere from Egyptian mythology to Greek mythology to a bunch of in-jokes. After awhile even famous and well-known literature gets in on the game. However, outside of the "Un-" sets, you'll still find a few easter eggs of unusual influence - two of which Magic itself has even specially noted. Specifically from the Innistrad block.
In 2017, Mark Rosewater was asked what his favorite Magic saster eggs were and he quickly answered "The Innistrad Plants vs. Zombie nod (Grave Bramble) and Jonathan Coulton nod (Creepy Doll) are both very cool."
So what are these cards? Well, we've already mentioned Grave Bramble.
In 2011, the computer game Plants vs. Zombies had supplanted Farmville as the most popular casual games, more-or-less holding on to the crown all to itself until the Candy Crush generation a few years later- certainly by the height of Angry Birds. While most games are hard to work into sets due to things like copyright and worries over cross promotion, Plants vs. Zombies would be relatively easier thanks to the prevalence of both already in the game. In fact, with an ability that said "Defender, protection from Zombies", Grave Bramble pretty much gave Innistrad the perfect 2011 pinnacle of hidden pop culture. It also didn't draw attention to it, with designers leaving it for players to figure out the connection.
The other card,from Portal. He also had a song called "Creepy Doll." As Innistrad was more horror-themed than anything else, designers went to include pretty much horror cliche in card form - after all they had just done killer plants in Grave Bramble. But they were missing old, creepy dolls. As serendipity would have it, it all kinda meshed together with his song and, well, it kinda created a much more obscure, yet recognizable, easter egg.
Of course, there were some more obvious inspired-by-horror-culture cards in the block such as Invisible Stalker (The Invisible Man), Civilized Scholar/Homicidal Brute (The Strange Case of Dr. Jekyll and Mr. Hyde), Nevermore (The Raven), and Cloistered Youth (The Exorcist), but those older references are for a story for another day.
Innistrad was really chock full of these, but even WotC couldn't resist going more obscure and more hidden with this deck. And, as it turned out, it made for some of their favorite even almost a decade years later.