From Wikipedia; "The series began with the pilot Rocky the Flying Squirrel. Production began in February 1958 with the hiring of voice actors June Foray, Paul Frees, Bill Scott, and William Conrad. Eight months later, General Mills signed a deal to sponsor the cartoon, under the condition that the show be run in a late-afternoon time slot, where it could be targeted towards children. Subsequently, Ward hired most of the rest of the production staff, including writers and designers. However, no animators were hired, since Ward was able to convince friends of his at Dancer, Fitzgerald, & Sample — an advertising firm that had General Mills as a client — to buy an animation studio in Mexico called Gamma Productions S.A. de C.V. (formerly known as Val-Mar Animation.) This outsourcing of the animation for the series was considered financially attractive by General Mills, but caused numerous problems. Bill Scott, when interviewed by animation historian Jim Korkis in 1982, described some of the problems that arose in the production of the series:
We found out very quickly that we could not depend on the Mexico studio to produce anything of quality. They were turning out the work very quickly and there were all kinds of mistakes and flaws and boo-boos. They would never check. Mustaches popped on and off Boris, Bullwinkle's antlers would change, colors would change, costumes would disappear. By the time we finally saw it, it was on the air."[citation needed]

As a child I didn't appreciate Bullwinkle enough. Now I do. Good post.