Congrats on your victory.
While I have never been hit with any of these, I have seen a number of projects and individuals hit with them. Of course they are also doing something with bigger IPs as well, like Star Wars, so I'm sure the bigger the IP you choose to play with the more likely they are to come down with at least a C&D.
The saddest part of these situations tends to be the amount of work the creators put into it. By the time they get notified, it could have been years of hard labor. Just "switching out" with some new IP they need to come up with in their head is just too much, too devastating, and the creator gives a tearful post and the project, regardless of how awesome it was, vanishes entirely.
People can also use those to attract talent as well. So sometimes the team wants to do this because they really love that particular IP, and don't want to put that much effort into something not that IP.