The man who plays Loveless' deaf-mute assistant is Leonard Falk... who is Robert Conrad's real-life father, making a cameo appearance.
Dr. Loveless enjoys a chocolate.
A drugged Jim lying unconscious.
: Artie eating a turkey leg.
The lake where Loveless’ boat sank… and ripples indicating the doctor may not be dead.
Michael Dunn almost died during the filming of the boat stunt at the end. Dunn insisted on doing his own stunts but caught his clothing on the boat edge as it sank. Only quick action by the crew freed him before he drowned.
Dr. Loveless appears in a wheelchair through the early part of the episode because the later sequences were filmed first. Michael Dunn injured his leg during the sequence with the lever in his laboratory, a sequence that was filmed early on in the production. Thus the doctor is in a wheelchair for much of the episode, or seated, or standing so his legs can't be seen.
Dr. Miguelito Loveless: Oh, Kitten, the things that are going to happen to his mind are fantastic. The strange things he'll see. I've just shoved him through a door into a world without rhyme or reason. His eyes will believe what his mind tells him too, and oh, what his mind will say. Just imagine. Now I'm finally powerful enough to control the mind of the invincible James West. Those whom the gods will destroy, they first make mad.
Dr. Miguelito Loveless: Alexander the Great, Caesar, Napoleon, all the great conquests of history mere child’s play compared to what I’ve done in that room with a shaving brush.
Dr. Miguelito Loveless: Oh, Kitten, it's so amusing the way men pride themselves on being civilized. But just four ounces of this, mixed with water, absorbed through the skin, and goodbye adieu ta-ta to all that veneer of civilization they prize so highly. Dissolved. And what emerges is the true nature of man. That primitive, murderous animal he really is, with absolutely no control over his feelings. A selfish beast. (checks the chocolate box) I.. wanted a candy, Kitten, and you've eaten all of them. Now I had my heart set on that. Ooh, fudge! Fudge, fudge! Fudge!
Dr. Miguelito Loveless: Not even a hello, Mr. West? I for one am overjoyed to see you. So much so that perhaps I shan't even kill you right at this moment. I'll wait ten seconds or so, perhaps. Time enough for me to sit here and enjoy your company. Ten precious seconds.
Dr. Miguelito Loveless: Ultimately we are all prisoners, are we not, Mr. West? Because we cannot escape ourselves. Stone walls are never so much a prison as the skin that surrounds each of us. Man's fate. My friend there is a deaf-mute.
Dr. Miguelito Loveless: I imagine you’re bursting with question
James: You’ll tell me.
Dr. Miguelito Loveless: How can you be so sure?
James: Because I know you. You’re always talking. About yourself. Bragging.
Dr. Miguelito Loveless: That’s preposterous. I’m not a petty man, I’m a scientist. I’ve trained, disciplined myself to be serenely dispassionate. To accuse me of bragging, you might as well accuse the sun of being egocentric because it shines.
Dr. Miguelito Loveless: Really, you can be quite exasperating. What kind of remark is that, "Um-hum"? I’m not quite sure why I put up with you.
James: Because you need me.
Dr. Miguelito Loveless: I need you? Now who’s being egocentric. I don’t need you, I don't need anyone, I have myself.
James: I thought I shot you.
Artemus: Well, you've done a lot of things to me in your time, but you never got around to that.
Dr. Miguelito Loveless: You are invincible. Is there anything you cannot do, any worlds you cannot make to live in.
Mirror Loveless: No, none. The world I wish for is the world I shall have.
Dr. Miguelito Loveless: You have spoken.
Dr. Miguelito Loveless: Do you know what tomorrow is?
Dr. Miguelito Loveless: The end of winter. Tomorrow everywhere except in the breast of man, the chill will begin to thaw. Small things, so fragile, will be born again. So much promise, and by the end of spring the promise will have flowerer. Mr. West, you cannot know the deep hurt one can feel when the seed cannot reach its full flowering. For in the summer Man comes, Man comes to… crush and maim and kill all that spring has given birth to. So summer must not come, nor Man. Man must be destroyed.
Artemus: You wouldn’t have any giblet gravy in your pocket, would you?
James: Ever kill a man with giblet gravy?
James: I’ll miss him. That little man with a giant rage against the whole universe.
Artemus: As Kitty said, who can blame the poor little one?
The episode title is a bit confusing since although Loveless' plan revolves around water, there is no spring, murderous or otherwise, that appears in the episode. The title becomes a little clearer late in the episode when Loveless talks about how spring gives rise to the small creatures of the world, and then Man rises in the summer to destroy them. But then that would be The Night of the Murderous Summer. So apparently the writers and producers were going for something that sounded properly sinister without it actually making sense in the episode.
Director Richard Donner makes use of mirrors throughout the episode, always as instruments of betrayal, deceit, and delusion. Jim originally shaves himself using a mirror, unaware that the very very act of shaving will betray him. Loveless observes him through a concealed one-way mirror. Later, Loveless deludes himself into believing that he is a giant, admiring his (imaginary) magnified image in a mirror. Finally, as Kitten bemoans her fate and her hopes that Loveless will love her, she sees herself as a beautiful bride in a mirror.