This episode was not good in the least , and I've been seeing that this season was pretty good and at the most these episodes were just okay.
But this is the first one I'd put on the level of an episode from the last 2 seasons. The plot is the biggest offender though, both plots feel recycled from episodes before.
The Stewie plot is decently similar to the Season 16 episode The D in Apartment 23 though not as good and there's nothing long term here, but Peter's plot is literally just the season 2 episode 'He's Too Sexy For His Fat' almost identical ideas.
Peter wants to help out Chris
Peter gets the fat sucked out of him
Peter neglects his prior goal of helping Chris
Peter loses his fat and in the end apologizes to his son.
At this point I feel like there aren't that many ideas left, shocking considering this is the 400th episode and for these milestones there's usually a really big or decently grandiose episode, something unique at least. Though no, this just feels like another random episode.
Another thing is the episode isn't funny, so far throughout season 21 I've laughed at least a couple of times. This time however I only laughed one time at the end.
I feel like the last 2 episodes or the first and second episodes of the season could've made for better 400th episodes.