IIRC, it was Nabisco that put out the cease-and-desist in the 1970s (e.g., Monsterettes (Oysterettes) was intended for the 9th Series, but not released until Wacky Pack Flashback in 2008), but that was only for their cookie and cracker products. Candy products were somehow immune from this (again, e.g., Soggy Babies (Sugar Babies)). I don't know what went on with Kellogg's back then, but in this day and age they've more than made up for it, as any one of us can see.
It seems to me that, after a few minor C&Ds from companies like, say, M&M/Mars in the first three ANS (which were obviously soon forgiven and forgotten), any and every product on the open market has been fair game for both Topps and Wackys from 2004 to this day.
Btw, JOJ, if you want more details on this subject, go to page 4 of this section (General Wacky Packages Discussion), look up the thread "What is the most parodied product among all Wackys?", go to pg. 2 and read both Reply #67 and 68 and then go to pg. 3 and read Reply #71. They should give you all the information you need.
