This has only happened on creative mode (I've only seen it there) but it might be on survival
I got out an ocelot, It looked at me and I gave him raw fish expecting a cat out of it,
But all I got was some hearts and a nice ocelot.
Steps to Reproduce:
1. Spawn ocelot, In a closed room
2. It look at you
3. you give it raw fish
4. Instead of turning into a cat it just has tons of hearts over its head when you feed it.
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It has to be a bit further away I think, and it has to approach you. Once it walks up to you, you can feed it and it will tame. Its a bit tricky.
i confirm this bug, i gave a ocelot 64 fish, and i he did aprproach me, a lot of hearts but no tamed ocelot. in case it realy is extremely tricky that the average minecraft can't even get a cat in creative than i think that the hearts or the fact that the ocelot accepts the fish are bugs.