A cartoon convention since the 1930s, the pentagram, or star outline, is often incorporated with other symbols to represent swearing, blasphemy, or scatalogical references.
Illustration detail from "Mode O'Day and her pals" Weirdo No. 9., 1983. Reprinted in The R. Crumb Handbook. R.[obert] Crumb (1943 - ) and Peter Poplaski. London : MQ Publications Limited, 2005. ISBN : 1-84072-716-0. 437p. p. 354