When I was a kid in school, I always had trouble swallowing the notion that life on Earth evolved in part from fish just spontaneously walking out of the ocean. Didn't seem terribly plausible to me. That was before I saw the walking catfish.
They really do just pick up and leave a pond when they feel like it, traipse down the street, and go to the next pond. If a pond starts to dry out in a drought, no problem, they'll just pack their bags and walk away. If they were just a little smarter, they'd be walking to the store to get cigarettes.
Some picky types say they don't truly "walk" but whatever, man, they're using their pectoral fins to propel themselves across the ground like the zombie on The Walking Dead that's missing the lower half of its body and crawling along using its hands while Rick gawks in awe. You wanna change the name to "The Crawling Catfish", be my guest; it sounds just as cool.
They apparently started out in Thailand, and over time made their way across Asia, then the Middle East, and then somehow wound up in Florida. (How do all these invasive species find out that Florida's the place to migrate? Do they have a newsletter?) Some have theorized that someone must have imported them for a home aquarium and then released them into the environment, but no one really knows for sure and the fish ain't sayin'. Wikipedia speculates, without source, that some say the infestation occurred when specimens somehow escaped from a truck transporting brood fish between Dade and Broward Counties. Perhaps when the truck driver pulled over to pee, a few of them saw their chance and made a break for freedom.
Tilapia farms used to keep their fisheries relatively open to the elements until they saw with horror that walking catfish were strolling out of the woods and marching right into their fish farms, saying "Hi guys!" and proceeding to eat their hosts. Now the farms have extensive fences erected to keep the walkers out, and possibly for good measure some signs reading "No catfish allowed."
(Tilapia, ironically enough, are also an invasive species in Florida that wildlife rangers dearly wish they could eradicate from the wild. Good luck with that.)
It's illegal to possess a walking catfish nowadays, thanks to overzealous lawmakers who don't seem to understand that Floridians don't possess walking catfish, walking catfish possess Florida. They walk among us. At this point you might as well just start issuing them driver's licenses.