These were very basic but appealing stickers because they were brilliantly simple: they basically showed some horrible-looking creature and gave it a common name like Bob or Betty. Naturally, kids hoarded or traded them out according to their and their friends' names.
The important thing to remember is that a particular image would be given more than one name. In the first series, most images have up to four different names associated with them; except for four cards: #29, #30, #32, and #40, which are easily distinguished by having colored or black backgrounds and have only one name. In the last two series, there are exactly two names for each image.
The second and third series stickers are identical, except that the second series have tan paper backs and the third series have thin white cardboard backs. The second series was released in about 1973-74, and the third series in 1976.
The stickers in the first series are numbered at the bottom right, but neither the stickers nor the cards in the second or third series are numbered.
The cards released with the second and third sets are puzzle pieces on the front, with a message on the back that read, 'Kids: Collect all 12 piecees to complete your ugly jigsaw puzzle.'
Additional names were released for the Canadian series one stickers, which can make collecting all of the U.S. names confusing. To further complicate things, a version of the first- series stickers was released in England with no names on them.
Collectors may of course choose to collect one of each image or every name, or every image.