Shorty Powers proclaimed himself as the "eighth astronaut". He enjoyed the limelight, and was accused of scheduling news conferences so he could appear live on national television and occasionally twisting the facts. He also put words in the astronauts mouths, such as the famous "A-OK" which he attributed to Alan Shepard. Shepard never said that and was unhappy with Powers.
Powers was thus "reassigned" after the Mercury program ended and resigned shortly thereafter.
Dennis's space mission in his dream is named "Menace I." This is perhaps the only time the word "menace" is mentioned during the series.
John Wilson's line "I wasn't living here last year" early in the series is the last direct reference in the series to the fact that he bought the house from George and Martha and had not always lived at 625 Elm Street. Several lines throughout the fourth season suggest that John and Eloise had lived there much longer than they actually had, and a few ignore the existence of George and Martha altogether.