Ethan says he's in the fourth grade.
A different actress (Cynthia Bond) plays Kate, the wife of Mark Harriton. In the earlier episode "Legacy" (#43) she was played by Angela Bassett.
There's lots of singing in this episode. Early on Peter Horton, Melanie Mayron and Mel Harris (Gary, Melissa and Hope) sing "Auld Lang Syne." Horton later sings the "Inchworm" lullabye and starts off a version of the Beatles' "In My Life" on which others soon join in. Most of the cast and guest stars participate in the singing of "Why Do Fools Fall in Love" and "Bye Bye Love." Unidentified (by me) voices sing "Blue Moon" and "Let the Good Times Roll" (the Shirley & Lee hit from 1957, not the similarly-titled song by the Cars from 1978.)
Patricia Wettig is credited but doesn't appear.