To find out where the Chick tract information comes from, just look at the sources mentioned in the tracts. Oftentimes, it comes from Kent Hovind, as well as the good old Bible, but there are also mentions of other people such as Scott Huse, in
this one for example.
I think that Jack Chick and other prominent creationists have very strong imaginations. That's the only place this stuff could have come from. Creationist literature spreads among the Christian community, and as their imaginative ideas spread, however false they are, they get reinforced. In the scientific community, such ideas are quickly struck down due to the availability of evidence to the contrary, but this does not happen among those who value faith more than evidence. Prejustices against those who believe in evolution are also reinforced, as people tend to dislike anyone who thinks differently from themselves, and these prejustices grow stronger and stronger until they reach the level seen in
Big Daddy and other tracts.