Children's book: little green monster under the porch

Trying to remember the title of a children's book we read in the 1980's about a scary monster that lived under a boy's porch. For most of the book, the monster remains unseen and towards the end, it turns out to be a small, cute, friendly, round puffball (furry) that can hang from a thread like a spider. And I think in the illustrations, it was smiling. Also, several- if not all- of the pages were a solid kelly green... the same color as the monster. Does this ring a bell for anyone? My sister and I are beginning to think we made it up.

Some overlap with Trigwater Did It by Lissa Rovetch, though it might be a long shot.

>2 beyondthefourthwall: Very close to the same color of green, but the "monster" was much smaller- about the size of a golf ball- and had no arms or legs. At least, not that I remember.

I know this book! I can see the pictures in my head, we read it many times as a kid. I have no idea what the title is, but I'll keep trying to remember.

@jeane So glad to know someone else remembers it... now we know we didn't dream it! Yes, please- if you remember anything else about it, please let me know!