Is it true that if you throw enough cats in the ocean, they will grow gills?

No.

But if you keep doing it for a few million years you will end up with a feline equivalent of a dolphin.

Assuming that you let the cats swim back to shore after you throw them in.

No, but if you geographically confine a population of cats in an environment where an aquatic lifestyle is the only viable option, over millions of years you may end up with a sea going pussy. Just like whales, dolphins, otters, seals, walruses, water voles, (not fully aquatic yet, but moving that way), water opposoms and many other terrestrial animals that have adapted to, or are in the process of adapting to life in the water. Perhaps the best example of this speciation is the land and marine iguanans.

And having gills would mean devolving the inner ears and lower jaw which were once part of the gill structure, but one advantage would be that that pesky laryngeal nerve would no longer have to loop down through the chest to get to the cats throat as it could go back to its original function: working the gills.

Edit: I can't believe they censored pussay.

Probably not. A whole order of mammals, the Cetacea, have adapted to living in the oceans, but none of them have grown gills.

Of course not. This happens over Millions of Years

Only if they're near a submerged Coca-Cola bottling plant in Atlanta

no, but its true that animals in an isoloted environment with high tides eventually will develop gills

I'm a dog lover, so this sounds like a very good experiment you could perform ...on many, many cats.

No - but if you throw enough christians into the grinder, they do turn into Pink Slime.

did you know if you stacked all the elephants in the world on top of each other they would die?

Certainly. Isn't that the main premise of evolution?