1st of 2 stories in Four Color #1152, titled Rocky and His Friends - Reprinted in Bullwinkle #4 07/1972, #15 03/1977 and #21 06/1979 - 8 pages:
Bullwinkle wants to be a music star but his singing is horrible. It is also throwing Pottsylvania's satellite out of orbit so Boris and Natasha must silence him.