My first evolving Pokemon!

So, my first Pokemon game was Yellow. I was treking through Vridian Forest, when I battled a very fast Caterpie! I caught it, of course! So, I go through more and I encountered a lv 14 Pideotto! It knocked out my Pidgey, Nidoran, and Pikachu! All I had left was my super fast Caterpie. GO CATERPIE! I made it use String Shot until the enemy was so slow! I used Tackle, and got a Critical Hit! I won! I earned 145 EXP! Then, it said Caterpie Is Evolving! I got a Metapod! Just so you all know, it is still fast.