There'll be sibling revelry at the Shubert Theatre Oct. 18 - Nov. 9 when Ernie Sabella joins brother David (or D.) in the smash revival of Chicago. Ernie will sub for a vacationing Joel Grey in the role of Amos Hart. Brother David just resumed playing Mary Sunshine after an extended hiatus to fulfill his opera commitments.

In an update to an earlier column, Liz Callaway, one half of the original "Sibling Revelry" duo, returns to Andrew Lloyd Webber's Cats on Sept. 22.

Kimberly Williams' last performance as Sunny Freitag in The Last Night of Ballyhoo will be Oct. 8; Arija Bareikis, currently at work on a movie, will return to the role of the "favored" cousin in Alfred Uhry's comedy/drama. The in-demand Bareikis can currently be seen in the independent film The Myth of Fingerprints, in which she plays Noah Wylie's estranged girlfriend. As a sidenote, Myth, which was cast by the Vineyard Theatre's artistic director Douglas Aibel, also features theatre regulars Blythe Danner and Hope Davis.

Prior to the start of performances, Frederick Weller replaced Robert Bagnell in Christopher Kyle's Plunge. Last season, Weller was seen on Broadway in Roundabout's The Rehearsal and Lincoln Center's The Little Foxes. Currently in previews, Plunge, Playwrights Horizons' inaugural production of its '97-'98 season, opens Sept. 28.

New additions to Smokey Joe's Cafe: James Beeks and Jerry Tellier have replaced Bobby Daye and Robert Neary, respectively. D'Atra Hicks is currently filling in for B.J. Crosby. Mary Testa has rejoined Forum after her month-long, enthusiastically-received stint as Madame Dilly in the Public Theater's On the Town in Central Park. Robert Fitch has taken over the role of Domina's beleagured husband, Senex, following the departure of Dick Latessa to join the incoming Proposals. As a footnote, David Alan Grier is contracted to stay with Forum til mid-November.

After her two-week engagement at Rainbow & Stars, Ann Duquesnay has returned to Bring in 'Da Noise, Bring in 'Da Funk. Lynette DuPre goes back to being Duquesnay's understudy.

Taye Diggs, Rent's resident landlord Benny, gave his last performance Aug. 31 and departed to star opposite Angela Bassett in the movie version of Terry McMillan's novel How Stella Got Her Groove Back. Jacques C. Smith joined the Rent cast as Diggs' successor on Sept. 12.

Billy Porter's lungs -- not to mention the rest of him -- have returned to the Eugene O'Neill Theatre as Grease!'s Teen Angel. Porter takes over from Kevin-Anthony. As a reminder, Lucy Lawless' last performance as Rizzo will be Oct. 19.

As reported elsewhere, Deborah Gibson joins Disney's Beauty and the Beast as Belle on Sept. 24. Production spokesman Patrick Paris did not know how long the former bubblegum songstress would remain with the musical.

Chloe Stewart has succeeded Roxanne Taga as Miss Saigon's Kim alternate. Stewart plays the title role in the Boublil-Schonberg musical Wednesday evenings and Saturday matinees.