The Return of Doctor X (1939). Trailer transcript below the fold.
My mother told me she saw a clip of this movie that showed Bogart petting a big floppy white rabbit and saying, "Many people have died, due to...due to...circumstances." She thinks it's the forerunner to Blofeld's cat and Monty Python's Flopsy ("There, poor Flopsy's dead, and never called me mother!"; the secret service dentistry sketch). I tried to find the Bogart bunny clip, but to no avail.
X—weird symbol of humanity’s most dangerous secret. The forbidden barrier that science must never cross! But in an amazing climax to a revolutionary medical discovery, its terrible power is delivered into the ruthless hands of a man the world once destroyed—a revenge-haunted genius, taking his name from the unknown inferno from which he returns. Dr. X: the mark of a madman who lives to kill. And who must kill to live!
Rosemary Lane: Dr. Xavier?
Bogart: Yes, I am Dr. Xavier.
Rosemary Lane: You can’t be!
Bogart: I’ll be very careful. I’ve always been careful—even though I had to kill.
Rosemary Lane: (whispers) You’re the blood killer!
Text on screen:
Back from the grave to find his betrayer! “The Return of Doctor X”
Text on screen:
Starring Humphrey Bogart in his strangest portrayal
Wayne Morris following his trail of TERROR!
Rosemary Lane, Trapped by his Lust for Life! Dennis Morgan, Leading Science’s Battle Against his Unleashed Fury!
Bogart: You told them about me!
John Litel: I didn’t have to —they found out for themselves!
Bogart: You’re lying!
John Litel: Shhhh!
Bogart: Does he know everything?
John Litel: No, only that I brought you back to life.
Bogart: I should really kill you, Flegg, for what you’ve done to me.
John Litel: Only give me a little longer!
Bogart: One week—that’s all.
Detective: There’s a killer loose in the city and you can help us find him
Lya Lys: I told you I don’t know anything
Detective: What about that fella Kane?
Bogart: What about Kane?
John Litel: My work ended not in failure, but in disaster! Disaster for me, disaster for Mr. X. The necessity for additional transfusions of human blood became increasingly frequent. Gentleman, I am responsible for the—[gunshot]
Text on screen: “The Return of Doctor X” Thrilling advance into life’s weird “No Man’s Land”!
It’s Memorable Exciting Different!