Paul Willson, later to play semi-regular barfly Paul, is here credited as a barfly named "Tom". However, he's never addressed by name in the actual episode.
The episode title refers to a 1961 Elvis Presley hit called "Little Sister". A phrase repeated several times in that song is "Little Sister, don'tcha do what your big sister done."
Carla: "I'm going to St. Eligius..." Carla tells the bar she's going to St. Eligius to give birth to her baby. This is the hospital featured in the fellow NBC show "St. Elsewhere". Two years later, Carla will appear on "St. Elsewhere" to tell the staff when they visit Cheers that St. Eligius was a rotten hospital to give birth to her baby in.