Green’s Dictionary of Slang

1. (US, orig. milit./medical) anyone who has suffered burns or actually burned to death.

1970		Current Sl. V:1 15: Crispy critter, n. Napalm victims.
1973		in C. Browne Body Shop 124: You ever see someone who’s been napalmed? [...] they call them ‘Krispy Krackers’.
1986		L. Heinemann Paco’s Story (1987) 15: Everything was transformed into Crispy Critters for half a dozen clicks in any direction.
1993		I. Rankin Black Book (2000) 47: There was a smouldering body as I recall. ‘Crispy batter’ we call those.
2002		J. Ellroy ‘The D.A.’ in Destination: Morgue! (2004) 140: The house ignites. Six crispy critters snap, crackle, and pop.

2. (US drugs) one who is under the influence of marijuana.

1975

cited in Spears Sl. and Jargon of Drugs and Drink (1986).