I was thinking about how many movies have crossovers. Like Freddy v Jason, Godzilla v Kong, Alien v Predator, etc. Yes, they’re basically all versus movies, but still. Comic books do it a lot too. But I was thinking, are there any book series that do this? The most I can think of is novelizations of movies or books already using established IPs. Authors often reuse their own characters, like Stephen King having the kids from IT show up in 11/22/63. But have separate authors ever crossed over their series with someone elses? Just thinking out loud here.
by Arcade_109