Not exactly a 'behind the scenes' picture...
A deleted scene from the end of 'Ghost Of Frankenstein' (1942) featured a brief shot the of the smoldering creature as it staggered across a field after escaping from the lab explosion. This would explain how it turns up alive in the next film, 'Frankenstein Meets the Wolf Man' (1943), although it doesn't explain how the creature came to be encased in ice!