I wouldn't call any of them SpongeBob "fans". We did grow up with SpongeBob though and SpongeBob is a common subject for Internet memes, so that might be it.
I wouldn't call any of them SpongeBob "fans".
There’s over 70k of them, how can you be so certain?
SpongeBob was originally for adults. But adults who grew up on Nickelodeon cartoons. Kids found it funny but don't always get the jokes because they are adult humor. They had to dumb it down for the kids. Before Netflix kids watched cable TV and Nickelodeon, and made a lot of memes about SpongeBob and the Krusty Crab. Every one of them wanted to work at the Krusty Crab with SpongBob and Squidward.
I associate "The Krusty Krab" to fake/secondary/tertiary/spam profiles. People I know personally and those I was able to confirm as legitimate profiles doesn't use that or any other fake information (or just leave it empty most of the time). I only see such fake information in accounts used to advertise their business in someone else's threads.
Culture / group related maybe? I have barely any friends on Facebook with real work details - a lot of them are made up. Especially doctors like to keep their profession (and real names) private.