Comic Title: Challengers of the Unknown #51
Publisher: DC (National Periodical Publications, Inc.)
Address: 575 Lexington Avenue, New York, NY
Cover Date: Aug/Sep 1966
On Sale Date: June 7, 1966 Newsstand Date June 7, 1966
Source: Direct Currents, Adventure Comics #346, Page 16

Copyright Date June 7, 1966
Source: Library of Congress, Periodicals 1966

Frequency: Bi-monthly
Cover Price: $0.12
Page Count: 32
Circulation: 221107
Editor: Murray Boltinoff

Title: "Smash the Sponge Man -- or Die"
Pages: 24

Feature(s):
Challengers of the Unknown (of Earth-1)

Writer: Bill Finger
Artist: Bob Brown

Feature Character(s)

• Challengers of the Unknown (last appearance in Challengers of the Unknown #50; next appearance in Challengers of the Unknown #52)
• Ace Morgan (last appearance in Challengers of the Unknown #50; next appearance in Challengers of the Unknown #52)
• Rocky Davis (last appearance in Challengers of the Unknown #50; next appearance in Challengers of the Unknown #52)
• Red Ryan (last appearance in Challengers of the Unknown #50; next appearance in Challengers of the Unknown #52)
• Prof. Haley (last appearance in Challengers of the Unknown #50; next appearance in Challengers of the Unknown #52)

Guest Star(s)

• Sea Devils (last appearance in Sea Devils #30; next appearance in Sea Devils #31)
• Dane Dorrance (last appearance in Sea Devils #30; next appearance in Sea Devils #31)
• Biff Bailey (last appearance in Sea Devils #30; next appearance in Sea Devils #31)
• Judy Walton (last appearance in Sea Devils #30; next appearance in Sea Devils #31)
• Nicky Walton (last appearance in Sea Devils #30; next appearance in Sea Devils #31)

Villain(s)

• The Sponge (aka Sponge Man; dies in this story; last appearance in Challengers of the Unknown #47; no further appearances)
• Scorpio (no further appearances)
• Lisa (name revealed in this story; last appearance in Challengers of the Unknown #47; no further appearances)

Other Character(s)

• Admiral Hutton and members of the U.S. military (no further appearances)

Synopsis:
When the army begins construction of a new underwater base, they disturb the Sponge. The creature that was once Miklos begins attacking. The Sea Devils are called in to help in the fight, but fail to subdue the creature. The Sea Devils then contact the Challengers.

Together the Challengers and the Sea Devils battle the Sponge. They finally subdue him and place him in a specially designed cell. Miklos's former neighbor Lisa comes by and is able to communicate with the Sponge. However, she is an agent of the underworld organization known as Scorpio. She releases the Sponge and causes him to hate the Challengers.

Scorpio plans to launch a poison gas missile near the army's construction site. The Challs arrive to stop them, but one of the missiles is fired. The Sponge catches the missile and absorbs the poison gas. He then sacrifices his own life to protect everyone else from the deadly poison.