Character mistake: In the episode where Henry has overdue library books, they are overdue by 5 years and 23 days. Both Henry and Monroe say in the episode that the fine is around $1000 (based on 10 cents per day due 5 years 23 days)... But in reality, using that calculation, the total would come to only $185, not $1000.
Too Close for Comfort (1980)
1 character mistake in show generally - chronological order
Starring: Nancy Dussault, Ted Knight, Deborah Van Valkenburgh, Jim J. Bullock
Genres: Comedy
Who Was That Baby I Saw You With? - S3-E7
Character mistake: After the mixup where a baby's grandmother took baby Andrew instead of her own grandson, in trying to track her down, Muriel mentions how since it was the baby's grandmother (instead of a parent), it would be hard to track her down because her last name would be different from her grandson's. This is not fully correct. Generally a baby will have a different last name than its MATERNAL grandmother, but the same last name of its PATERNAL grandmother, so Muriel's comment was only half accurate.