Maine
the most common place to find penguins is in Antarctica
japan
On a doorknob
a forest or the woods
In the ocean.
At a pet store!
Africa
Underground
corn and potatoes
There is no most common place to find Suicune (sometimes misspelled as suicun) in Pokémon FireRed. Where it goes is totally random.
Most of the hydrogen in the universe is contained in stars.