For a dumb farce, the plot is fairly complicated, so pay attention: Married Marjorie (Kirstie Alley) has a single sister, Jeanine (Jami Gertz), who thinks Marjorie should have an affair because her doctor husband, Harry (Scott Bakula), neglects her. Harry's dominating doctor sister, Iris (Carrie Fisher), also treats Marjorie as a housewife nothing. In rebellion, Marjorie picks up a stranger named Charles (Sam Elliott) for a thrashing hotel one-nighter, but Charles's heart gives out from the exertions. Then Marjorie learns that Charles was really Harry's brother, just returned from years overseas. So Marjorie tries to make it look like Charles committed suicide. She is aided by Nick (Bill Pullman), a bumbling window-blind salesman who just happened to be hanging blinds in Charles's hotel room. Nick doesn't want any bad publicity either, since his brother, Wilbur (Ed O'Neill), is a cop running for chief of police.
Get it? Everybody's raging and related. Screenwriter Martha Goldhirsh is betting that we can all relate to that. And for a while, we can. The game actors, most of them veterans of TV sitcoms, appear willing to try anything for a laugh. There hasn't been so much popeyed mugging since the Keystone Kops.
But the huffing and puffing grows tiresome, then irritating, then unendurable. Director Carl Reiner seems to have lost the dark undertones and sharp pacing he brought to Where's Poppa?, The Man With Two Brains and All of Me. His latest has the cheesy, done-on-the-run feel that damaged Summer School, Summer Rental and Bert Rigby, You're a Fool. All the shouting in Sibling Rivalry will leave audiences exhausted or ready to shout back.