The Flashback series is the second Garbage Pail Kids set to contain Sketch cards numbering 1/1 (one-of-a-kind, found one out of every ten hobby or retail box). Ten artists worked on the Sketch cards for this release; veteran artists Jay Lynch (1070 sketches) and Tom Bunk (242 sketches); next-generation artists Brent Engstrom (260 sketches), Dave Gross (260 sketches), Fred Wheaton (200 sketches), Layron Dejarnette (250 sketches), Mark Pingitore (210 sketches), Jeff Zapata (140 sketches) and Colin Walton (103 sketches); and newcomer Joe Simko (500 sketches). Besides the sketch cards located within the boxes, the artists were also given 10 blank sketch 'Return' cards from the Topps company, and once approved, could be kept, sold or auctioned — these sketch cards are often more highly detailed. James Warhola's artwork shows up on the back of the sketch cards which is the original artwork for 486a/b of the 12th series GPK.