It's sophisticated enough for kids, simple enough for adults

Shinbone Alley (1970)

Suicidal poet Archy tries to end his life by jumping off a bridge, but awakens to find he has assumed the life of a cockroach and has become a part of a community of creatures living in a newspaper office. He also discovers that he can still write poetry, using a typewriter, and begins to enjoy his new life. Archy develops deep feelings for the lovely but self-destructive cat Mehitabel, but will have to fight to win her from bad-boy tomcat Bill.