It's not a re-re-ruin; it's John being an idiot.
Panel 1: We start off with him tripping over a screwdriver. As he falls on his Patterkiester, his cry of AAAAHH!!! is so loud, it fills the panel behind him.
Panel 2: Now that he's quieted down, we see where he is: on the steps of his back porch. As Elly is about to rake up Lizzie and put her in a yard bag, he asks who left this f**!!@@$ screwdriver on the stairs.
Panel 3: She leans over him and tells him, as he holds the part of his head that got nailed, he did.
Panel 4: He responds to being reminded he's an idiot by asking her to for heaven's sake remind him to be more careful.
Summary: The 'joke' is that Elly is supposed to be John's mommy too. What's more, this child will never grow up. (Especially given that he's suffered a brain-scrambling concussion.)