http://www.bonethefish.com/viewtopics.php?409

Widower Anthony Morton "Tony" Micelli (Danza) is a former second baseman for the St. Louis Cardinals who was forced to retire due to a shoulder injury. He wanted to move out of Brooklyn to find a better environment for his daughter, Samantha (Alyssa Milano). He ended up taking a job in upscale Fairfield, Connecticut as a live-in housekeeper for divorced advertising executive Angela Bower (Judith Light). The Micellis moved into the Bower residence. Also starring were Danny Pintauro as Angela's son Jonathan and Katherine Helmond as Mona Robinson, her feisty, man-hungry mother.

Boned the fish' seriously?

it was done/dusted boned as you says
the day bill show up in season 7 out nowhere and disapear the same way
season 8 was geting good after bill disapear

The obvious go-to answer right away is to say that Billy was the jump the shark/boned the fish moment. But even on the old JTS website (https://web.archive.org/web/20070110201047/http://www.jumptheshark.com/w/whostheboss.htm), Billy's arrival was maybe, only the fourth most voted category.

And in fairness, Billy was only there for a single season (the second before last), so it isn't like his character did any real irreparable damage to the show. He was just an awkward and annoying little side character and experiment that the producers eventually figured out didn't exactly work.

Having rewatched the series on GAC Family over the past year or so, if you asked me, I think that Who's the Boss? really "jumped the shark" when Alyssa Milano dyed her hair jet black, got bangs, and cut it to shoulder length starting with the "Supermom Burnout" episode (which I believe was the sixth or seventh episode into the sixth season).

I know that this is going to sound silly, but Alyssa was a big reason I believe, why many kids and teenagers (especially young boys) at the time watched the show. Her radically and randomly altering her appearance (I almost consider the black hair to be Sam's "goth look") when at that point, she really shouldn't (at least in my mind) in the middle of the season, was a clear indicator that show's overall tenor was going to change going forward. And of course, Alyssa had to cut her hair even shorter, thus further neutering her beauty and sex appeal.

And sure itself, it was shortly thereafter, that the producers and writers came up with the "brilliant" idea and suggestion of having Sam skip her senior year in high school and heading straight to college. It was as if the writers were in a rush to age and mature Sam's character instead of continuing to plot storylines organically. And this continued all the way through the final season, where they had her marry some random guy that we barely knew.

If anything, Sam marrying Hank was a bigger "jump the shark" moment over Billy because at least, you could in theory, easily write Billy out and act like he never existed. You couldn't exactly do that with Hank since he was now Sam's husband. I'm guessing that because he came along right towards the very end of the series (instead of being there virtually the entire season like Billy was the year before), he isn't scrutinized as much. It's also much easier to pick on Billy because he fit in the tried and true "Cousin Oliver" (https://tvtropes.org/pmwiki/pmwiki.php/Main/CousinOliver) trope.