But, girls... you asked for the truth... and you got it! 
Superman #176 is an issue of the series Superman (Volume 1) with a cover date of April, 1965.
Synopsis for "The Revenge of the Super-Pets!"
To learn why the late Mark Dane left his fortune to be used for an animal shelter to atone for his uncle Cyrus Atwill's unnamed wrongs, Superman takes the Legion of Super-Pets back to the 1860s where they learn of Atwill's abuses against animals and help teach him a lesson, with the help of ASPCA founder Henry Bergh.
Appearing in "The Revenge of the Super-Pets!"
Featured Characters:
- Superman (Adopts the temporary alias of Superb-O the strongman while in the 1860s)
Supporting Characters:
Antagonists:
- Cyrus Atwill (Single appearance)
Other Characters:
- Henry Bergh
- Mark Dane (Single appearance) (In picture only)
- Saturn Girl (Mentioned only)
Locations:
- 1965
- 1860s
- Metropolis
- Atwill's Junkyard
- Metropolis
- Timestream
Items:
- Horseshoes
Vehicles:
- Horse-Drawn Carts
Synopsis for "Tales of Green Kryptonite No. 2"
The chunk of Green Kryptonite goes on to relate how, after a planeful of journalists had engine trouble in the Arctic, Clark Kent was briefly weakened by the Green K and later decided to construct his permanent Fortress of Solitude there. Later, a professor learned how to make Kryptonite non-deadly to Superman by a radiation treatment. However, the treatment was only temporarily effective, and would make the treated Kryptonite deadly to normal humans. Thus, Superman destroyed the professor's apparatus and used giant tongs to throw the Green Kryptonite into space. It passed through the red cosmic cloud that transformed it into Red Kryptonite and sent it hurtling back towards Earth.
Appearing in "Tales of Green Kryptonite No. 2"
Featured Characters:
- A sentient chunk of Green Kryptonite (Transformed into Red Kryptonite) (Flashback and main story)
Supporting Characters:
Other Characters:
- Jimmy Olsen (Flashback only)
- Krypto (Mentioned only)
- Lois Lane (Flashback only)
- Perry White (Flashback only)
- Professor Clyde (Single appearance) (Flashback only)
- Supergirl (Mentioned only)
Locations:
- Earth
- Arctic Circle (Flashback only)
- Fortress of Solitude (Origin)
- Metropolis (Flashback only)
- Daily Planet (Flashback only)
- Metropolis Airport (Flashback only)
- Smallville (Flashback only)
- Arctic Circle (Flashback only)
- Krypton (Destroyed in Flashback)
Items:
- Aurora Borealis
- Professor Clyde's Anti-Death Ray (Single appearance) (Flashback only)
- Green Kryptonite
- Red Kryptonite
- Long Leaden Tongs
- Parachutes
Vehicles:
- Airliner
Synopsis for "Superman's Day of Truth!"
Superman and Supergirl win no popularity contests in Metropolis or Midvale when, for one 24-hour period, they tell the unvarnished truth or give their honest opinion whenever asked.
When Superman has to testify at a trial, the lawyer for the plaintiff insists on having him write his secret identity's name on a blackboard--which he does, but at such super-speed that the blackboard melts from the friction before anyone can see it. When asked to give the location of his Fortress of Solitude, Superman gives the coordinates for his long-abandoned underwater Fortress.
Finally, Supergirl and Superman shrink themselves and go to Kandor, where they and the Kandorians celebrate the Day of Truth. This is a holiday observed in honor of the ancient hero Val-Lor, who spoke up boldly against the Vrang invaders who oppressed Kryptonians, died for his words, and sparked a revolt that liberated Krypton. Later, Superman and Supergirl reveal what they had to do to their friends, and are forgiven.
Appearing in "Superman's Day of Truth!"
Featured Characters:
Supporting Characters:
- Jimmy Olsen
- Lana Lang
- Lois Lane
- Lucy Lane (Mentioned only)
- Perry White
- Professor Potter
- Supergirl (Flashback and main story)
Antagonists:
- Vrangs (First appearance) (Flashback only)
Other Characters:
- Atlanteans
- Brainiac (Mentioned only)
- Kandorians
- Supergirl Fan Club (Flashback only)
- Kryptonians (Flashback only)
- Val-Lor (First appearance) (Dies in flashback)
Locations:
- Earth
- Atlantis
- Tritonis (Unnamed)
- Fortress of Solitude
- Metropolis
- Midvale (Mentioned only)
- Atlantis
- Krypton (Flashback only)
- Jewel Mountains (Flashback only)
Items:
- Blackboard
- Kryptonian Book of Deeds
- Parachute
- Professor Potter's Onion Squeezing Device
- Red Kryptonite (Mentioned only)
- Val-Lor (Statue only)
Vehicles:
- Vrang Spacecraft (Flashback only)
Notes
- "Superman's Day of Truth!" was reprinted in Superman #241.
- The ASPCA is mistakenly referred to in "The Revenge of the Super-Pets!" as the SPCA.
Trivia
- In the origin of the Fortress of Solitude, Superman is clearly digging through rock, indicating that his fortress is somewhere in the Arctic Archipelago and not at the North Pole, where there is no land.
See Also
Recommended Reading
- Superman Family Recommended Reading
- Action Comics (Volume 1)
- Adventure Comics (Volume 1)
- DC Comics Presents (Volume 1)
- Superboy (Volume 1)
- Superboy (Volume 2)
- Supergirl (Volume 1)
- Supergirl (Volume 2)
- Superman (Volume 1)
- Superman Family (Volume 1)
- Superman's Girl Friend, Lois Lane (Volume 1)
- Superman's Pal, Jimmy Olsen (Volume 1)
- World's Finest (Volume 1)
Links and References
"Superman's Day of Truth" Review on Comic Box Commentary