Roger Willis character in Boys! Raise Giant Mushrooms in Your Cellar

I was watching Boys! Raise Giant Mushrooms in Your Cellar and I noticed that the actor that played Roger Willis was Tom McBeath. I recognized him from Stargate SG-1 where he played Col. Harry Maybourne. However, in the credits Roger Willis is credited as Frank C. Turner. How can this be? Watch the episode and see for yourself. I wonder if Tom McBeath is aware of this.