What does this story mean?

Alright, so my friend told me a story last week and I do not understand the meaning to it. Here it goes:

There is a lion and a kitty. The kitty is big fierce and strong while the lion is not. One day the lion asked the kitty to train him, so he did. The lion finally became this buff cat and said to the kitty, “Now I can destroy you!” Then the kitty responded, “No you can not, I did not teach you everything.” And he runs away.

Why is it a lion and a kitty? I have no idea, but my friend told me that the meaning of this story may help me in the future, but I really do not understand this.

Any ideas?