 The siblings also appeared as co-hosts of the fall 1978 "ABC All-Star Saturday Preview Special", a youth-oriented sketch comedy show featuring musical guests such as the Bee Gees and Donny Osmond.McNichol and his sister, however, ceased performing together after Kristy had a manic breakdown while the two were in France; she was diagnosed with bipolar disorder.Afterward, McNichol stepped away from the music industry, later commenting