Revealing mistake: When Ted Dansen gets buried in the sand, there isn't any extra sand piled up that was displaced by his body being in the hole.
Continuity mistake: Near the end of the "Father's Day" story, Sylvia gets impatient and goes to the kitchen calling to Mrs. Danvers. She sees the muddy footprints and investigates further. Mrs. Danvers' corpse falls against the back of the kitchen door with her face in the round window. As Sylvia lets go of the door, you can see the dead Mrs. Danvers blink as she slides across the window out of view.
Other mistake: The creep tells us that this is the first issue, but mere seconds after the famous ending of Father's Day we see fan mail on the second page, impossible for the first issue. (00:21:05)
Richard Vickers: I'll shoot you dead.
Harry: You can't shoot us dead, Richard.
Becky: ...because we're already dead.
Harry: We want to see you, Richard. We dug a hole for you, Richard.
Becky: ...on the beach.