Professor Bob is an evil scientist who appeared at the end of "Operation A.R.C.T.I.C", where it is revealed that he, rather than Professor XXXL, whose lab is next door to his, is conducting an operation that will eliminate all snow days from schools.
When Professor Bob is seen, he claims that his machine is complete, and his evil plan presumably succeeds.
He also made cameos in "Operation: M.O.V.I.E.", "Operation: A.F.L.O.A.T.", "Operation: U.T.O.P.I.A.", "Operation: A.W.A.R.D.S.", and "Operation: Z.E.R.O.".