In this E. R., you never know who's going to show up (1984)

 This Christmas episode of E. R. finds the staff having to work through a blizzard. Dr. Sheinfeld (Elliott Gould) learns that his daughter (Pamela Seagall) wants to move in with him instead of with her mom and a prospective stepdad.

George Clooney (ex-The Facts of Life) debuts as a new doctor, who's a bit of a ladies man. MTV doll Martha Quinn appears as herself, nursing an injury. Turns out Jenny (Seagall) is a huge fan. Jason Alexander appears briefly.

Unfortunately, while the full episode is available, it is in poor quality, so this excerpt will have to do.

Countdown to Christmas: Jingle Bells (1953)

 From The Ed Sullivan Show:

Julius LaRosa made a number of appearances in 1953 alone on the program, and for the holidays, he serves up this rendition of "Jingle Bells":

Countdown to Christmas: Merry Gentlemen (Lucas Tanner, 1974)

 Lucas Tanner (David Hartman) has an unexpected meeting with his former father-in-law (guest star Barry Sullivan) as the holidays approach, reminding Tanner of the family tragedy he had suffered. Here's "Merry Gentlemen":

No rating. Just a public service.

What Might've Been: Everything's Relative (1987)

 Two brothers share a loft, and chaos ensues, especially when their mother gets involved.

Everything's Relative didn't even finish its lone season in 1987. Had it done so, and had it been a hit, then Jerry Seinfeld would've been looking for someone else to play George, since Jason Alexander wouldn't have been available.

Alexander toplines as Julian, the elder of the two brothers, and divorced. Our cast also includes Anne Jackson and Gina Hecht (ex-Mork & Mindy). Let's take a look at a sample episode.

To think that Alexander had graduated from commercials (i.e. McDonald's), but it'd be another year or two before he achieved icon status.

No rating. Just a public service.