Watchog doesn't have an evolution. It's the final evolution of Patrat, which it evolves from at level 20.
Patrat will evolve into Watchog when it reaches level 20
you evolve patrat on level 20
He evolves into watchhog.
If you mean WATCHHOG he doesn't evolve. he is the highest form you can get.
It is suppose to evolve at the Level of 20,but if you want it to evolve later it can evolve anything after it is at Level 20.
It will evolve by level. Teddiursa will evolve into a Ursaring at level 30.
They evolve at level 36
It will evolve at level 36.
They evolve on level 40
it evolve on level on 64
To evolve a Sandshrew level it up to Level 22 and it will evolve into Sandslash.
Pikachu do not evolve by level. They evolve when a thunderstone is used on them.