The special guest star is always simply referred to as "Superman". Nowhere in the script does anyone actually say "George Reeves as Superman". (The ending voiceover originally gave credit to George Reeves, but it was removed in syndication.) It is believed that the intention was to avoid confusing children or "bursting their bubble" by letting them know that Superman was a fantasy character played by an actor.
Madge Blake, who thinks she sees Superman on the ledge, would later play Aunt Harriet Cooper in the 1966-1967 Batman series.
Doris Singleton, who plays Caroline Appleby, appeared with George Reeves in his "Superman" TV series, four years prior to this airing.
In both this episode and Superman III (1983), Superman is asked by a mother of a boy named Ricky to attend a birthday party for him.
Although Lucy and Caroline had a long-standing competition over who had the cutest child, this is the only time it's mentioned that the boys were born four days apart.