While Shaggy is driving to Pingree's, his eyes are closed and then open for a second. Normally, the opposite should happen.
General Hepler wanted to use civilians to locate Myrtle, in order to be as inconspicuous as possible. So he chose the "most normal" people who entered the store: a six-foot tall beatnik, a redheaded bombshell, a gigantic *talking dog*, and another talking dog who *walked upright.*