"So what 1975 comic book have you been mining these great ads and such from?” you ask. Here it is… Plop! “The Magazine Of Weird Humor!”, which was produced between 1973 and 1976 by DC Comics.
What you should see right off is that the art on this cover was done by Sergio Aragonés of MAD Magazine and Marvel’s Groo The Wanderer with special guest Wallace Wood of classic MAD Magazine fame who was also responsible for Marvel’s Daredevil wearing a red costume… yet this was a DC line. The three characters in the upper left (Cain the devil, Eve the witch, and Able the demon) were the heads which appeared in the first and last panel of every story as narrators similar to Rod Serling on The Twilight Zone.
This issue was mentioned in the Wikipedia article as containing the Steve Skeates written/Steve Ditko and Wallace Wood illustrated story “Love is a Dandy!”, which is vaguely related to “Little Shop of Horrors”. A man named Hubert who has no luck with people finds a dandelion in the sidewalk (which he names Dandy) that he falls in love with; the feeling is mutual, and he even meets her parents to discuss their “living in sin”. The weird[er] twist is that he has a persistant female friend Melody who is a vegetarian and, on the last page of the story, makes steamed greens out of his beloved plant… this drives him into a murderous rage, and in the final panel the white-coated gentlemen from the lunatic asylum have come to take him away (ha ha!).