The Showcase series featured characters in either one-shot appearances or brief two or three issue runs as a way to determine reader interest, without the financial risk of featuring "untested" characters in their own ongoing titles. The series saw the first appearance of several major characters including the Silver Age Flash, the Challengers of the Unknown, Space Ranger, Adam Strange, Rip Hunter, the Silver Age Green Lantern, the Sea Devils, the Silver Age Atom, the Metal Men, the Inferior Five, the Creeper, Anthro, the Hawk and Dove, Angel and the Ape, and Bat Lash.