1 bulbasaur
2 ivysaur
3 venusaur
4 charmander
5 charmeleon
6 charizard
7 squirtle
8 wartortle
9 blastoise
10 caterpie
11 metapod
12 butterfree
13 weedle
14 kakuna
15 beedrill
16 pidgey
17 pidgeotto
18 pidgeot
19 rattata
20 raticate