How many movies have Frank Welker and Glenn Leopold collaborated on?

They have worked on 5 movies together! Their first movie together was Scooby-Doo and the Ghoul School (1988) while their highest rated movie together was Scooby-Doo on Zombie Island (1998). They have not worked together since Scooby-Doo and the Alien Invaders (2000). They are most known for their family films together.