It’s been almost 20 years since I’ve watched Voyager. Can someone remind me what the context is for this meme?
Same. I vaguely recall something about these two de evolving into catfish with legs (a prior meme post is the only reason I remember anything) and… I am going to guess they made legged catfish babies or something.

Tom uses a shuttle to travel to warp ten. Once he reaches the threshold he’s everywhere at the same time, becomes Kwisatz Haderach. When he comes back he starts mutating, loses his mind, kidnaps the captain, they fly off at warp 10.

By the time voyager finds them they’ve devolved(or evolved) into small amphibians, luckily the do has a magic serum that will fix them. As the crew are about to leave they notice a bunch of tadpoles. Basically Tom and Kat had tadpole babies.

I always thought it was evolved, which I didn’t understand at all.
You didn’t understand it because it just didn’t make sense. There is a very good reason why it’s one of the most poorly rated episodes across all of trek.
Animals Keep Evolving Into Crabs, and Scientists Don't Know Why

Crabs have evolved at least five separate times, and the process for adopting a crab shape is so popular it even has a name—carcinization.

Newsweek
It was, and it doesn’t make any sense. That’s not how evolution works lol, the writers really should’ve gone with mutating instead
If there’s one thing Trek is totally consistent about, it’s the writers having no fucking clue what evolution is.
If you really want to remember
In case you are masochistic enough to seek this episode out, it is season 2, episode 15 of Voyager, “Threshold”