The original Chewits advertisements featured the ‘Monster Muncher’, a Godzilla-resembling mascot on the hunt for something chewy to eat.  But the ‘Monster Muncher’ could only be quelled by a pack of Chewits. They used claymation special effects, and also included a voiceover style reminiscent of a 1950s radio serial.

The walls have ears.

“Ere, 2 extra Chewits are still only ten pence!
Ssshhhhh!!
Remember, loose talk costs Newsagents!
Chewits.
CHEW for VICTORY!”