The 5th Series has two puzzles that can be formed using the backs of 21 cards. There are 2 card backs that feature a puzzle preview for each of the puzzles. The caveat is that the two puzzles cannot be completed from an 80-card set. There are 8 cards with 2 back variations required to complete both puzzles in this set. 4 of the cards are used in Puzzle D and the other 4 are used in Puzzle E. The 4 variations used in this puzzle are #168b, 169b, 175b, 178b. If you want to be able to complete both puzzles, then you're going to want the 88-card master set for the 5th Series of GPK.
Jordan Nuts, Terri Cloth, and Johnny One-Note have doubles in this puzzle and are located at the top-right and top-center. Blue-Boy George's back variation is actually a character profile for Acne Amy, so you could actually complete both puzzles with an 86-card set, but you'd have to have the right versions of #178a/b.