Here are the front and back of a 1955 package of Post Sugar Crisp cereal. Featured here is an offer for patches of 15 of the then-16 Major League Baseball clubs, minus the newly-transplanted Kansas City Athletics, late of Philadelphia.
Here's a 1951 magazine advertisement for Post Sugar Crisp cereal, which had just gone on the market. This ad features the Three Sugar Bears, Handy, Dandy, and Candy. By the early 1960s, they would be replaced as spokesmen for the cereal by some pimp-smooth sweater-wearing character came across as a combo of Bing Crosby and Dean Martin.
Here's another 1950s TV commercial for a Post cereal, this time, Post Sugar Crisp with both Roy Rogers and Dale Evans. In this one, the 3 Honey Bears (Handy, Dandy, and Candy) try to help Dale as they produced a new, unopened box of the cereal before Roy lumbers in for breakfast.
But eating Post Sugar Crisp apparently does, as this early-1950s commercial, which aired during a DuMont Network telecast of Captain Video and His Video Rangers attests.
In this 1960s television commercial, Granny Goodwitch (voiced by Ruth Buzzi) tries to hide her box of Post Sugar Crisp from the reach of that pimp-smooth Sugar Bear (voiced by Gerry Mathews), but, to no avail.
Sugar Bear was one of several characters associated with Post Cereals featured on the old Linus The Lionhearted cartoon show, first-run episodes aired on CBS from 1964-66.