The most famous episode of the show anymore seems to be the dead-serious one from about 1992 or so where Aunt Jackie gets beaten by her boyfriend and John Goodman (off-screen) goes off and pounds the guy's face in; it's actually a dreadful load of lunkheaded audience-pandering bulls*** and I've always hated it.
Re: John Goodman - He was often used rather poorly by the show and fought with Roseanne all the time and it's been said that hanging out with Tom Arnold caused Goodman to get into drink and drugs and I've always been of the impression that his Coen Bros. roles, which used him spectacularly (I think he said he considered Barton Fink a career high) caused him to want to be off the show maybe four or five years into its run. He ended up leaving for most of the last two seasons, pulling a Duchovny and only coming back for the last couple of episodes.
Regarding him having "better things to do," he gave one of his career best performances recently in 10 Cloverfield Lane, go see that if you haven't. He was also in Kong: Skull Island which nobody here seemed to be interested in.