Face of the Frog

Ella Bennet (as Eva Anthes)

Philo Johnson

John Bennet (as Karl Lange)

Joshua Broad

Lolita

Ray Bennet

Ezra Maitland

Sergeant Balder aka Nummer 7 (German version) / Sergeant Barclay aka Number 7 (English version)

Sir Archibald (as Ernst W. Fürbringer)

James

Everett

Lew Brady

Mills

Lady Maggie Farnsworth (German version) / Lady Aubrid Farnsworth (English version)

(Ober-) Inspektor Elk (German version) / (Chief) Inspector Hedge (English version)

Inspektor Genter (voice) (uncredited)

Inspektor Genter aka K 297 (German version) / Inspector Higgins (English version) (uncredited)

Voice of Newsreader on Radio (voice) (uncredited)

Sergeant Rubby (uncredited)

(uncredited)

Lord Charles Farnsworth (uncredited)

Most of the outdoor scenes were shot in Denmark.

The idea of creating a German Edgar Wallace-Adaption for the screen came to 'Walfried Barthel', then head of Constantin Film, and Constantin's scenario editor Gerhard F. Hummel after a private screening of Guy Hamilton's film of The Ringer (1952).

When inspector Elk/Hedge is riding in the Double Decker Bus near the beginning of the film, the signs near his window are mirror inverted, indicating a flipped shot. They obviously shot the scene (in front of a very obvious rear-projection) as if driving from left to right but found out that it didn't intercut well with the outside shot of the real bus going the other way.

When they watch the film that Richard Gordon shot in the nightclub, the lower reel of the projector is not moving. It should be, otherwise the film already passed through the projector would be dumped on the floor.

When Richard Gordon and his butler James start the training fight while being held captive at the Frog's, there is suddenly a carpet on the ground, covering the mattress that softens James' fall. The carpet even covers the lower part of the door. In the next shot, the carpet is gone.