Spike accidentally gets a taste of meat. Fortunately Lero is living in Ponyville, and with his human background can give Spike some friendly advice. And then... Well. Who knows what might happen?
Spike blushed. "Oh, Lero-Sempai, I was so confused! I knew I had to come to you for advice."
Lero was very confused about how Spike had even learned the word 'Sempai.'
Then they waited until Spike was a teenage dragon, then had sex.
And then Spike became a man.
And then Spike became a man.