In the episode where Hal and the boys go to the race track, they come home to discover that Lois had gone through all of their stuff, in that pile was a pack of Morley cigarettes, the same fake brand the Cigarette Smoking Man prefers to use on The X-Files.
Jane Kaczmarek in real life has given birth by way of Caesarian section three times. When it came time to simulate giving birth without a C-section in the episode Baby Part Two, Jane just imitated every other birth she had seen on television.
In the opening credits, the boxer who inadvertently knocks out the referee is Pedro Cardenas, fighting Willie deWit. He accidentally KO'ed referee Bert Lowes during the 1982 North American Championships in Las Vegas.
Actor Patrick Bristow first appears in the Episode "Ida's Boyfriend" as Phillip, the head of the Acting troupe hired to hold a Murder Mystery at the Grotto. Later, Patrick Bristow returns to the show as Lloyd, Chad's Father in the episode "Chad Sleep's Over".
None of Malcolm's family have a last name. While in military school, Francis was referred to only as "Francis" and never by his last name. Reese joins the army and we learn the last name of his fake ID is "Jetson" but there is no indication that that is his real name.
Although the family's surname was revealed as Wilkerson in the pilot episode, it was decided afterwards that the family shouldn't have a last name. A running joke on set was that the family's last name was 'Nolastname'. This is officially confirmed in the final episode "Graduation" when Francis drops his work pass and his surname is briefly seen. Further confirmation can be seen when Malcolm is introduced to the stage for his speech. His last name is not heard as the microphone screeches at the crucial moment but you can read the announcer's lips clearly saying 'Malcolm Nolastname'.