Goof: At the end of the episode, when Ellery gathers the suspects, he addresses the observing O'Neill as "Maddie" or "Mattie". In the credits, he is listed as "Knucks" O'Neill.
O'Neill: Now remember, Sam, Mr. Anthony wants everything to go smooth.
Hatter: Look, he didn't have to send you around here to tell me that. Now, will you beat it before Flannigan sees you hanging around the Kid?
O'Neill: Flannigan don't know me.
Hatter: Flannigan knows everybody.
Inspector: You know, when you're working on a book you're great company. Course, if I want conversation I can always talk to the goldfish.
Ellery: Oh, that's nice.
Inspector: On second thought, the goldfish might make more sense.
Ellery: Dad, your coffee's worse than mine.
Inspector: This is your coffee. I heated up what was leftover from breakfast.
Ellery: Well, I heated it up from last night's leftovers. And, I'm not really sure it was fresh then.
Inspector: What are you doing in the kitchen?
Ellery: Oh, I just heated up some coffee.
Inspector: I hope it's today's. Or even this week's.
Otis Young's most famous role is that of Petty Officer Mulhall in the 1973 film The Last Detail.
Jerry Quarry was a leading heavyweight boxing contender in the late 60's and early 70's.
Robert Alda was the father of M*A*S*H star Alan Alda.