Common phrase for-- This is not a common phrase. "Wahey" is-- is... pointless. Not even people who have fits of joy who say "Wahey!". In fact, there is only one person who says "Wahey!" but his name shall not be revealed, or he will have to kill you.
Person A: Hey, check it out! I found 400 dollars on the ground!
Wahey Wielder: Wahey!!
Person A: Uh-- ok?
W.W.: Wahey!! Moop! Fiibit! Fibit!
Person A: Goop!