1. Who was Superman's son? (Real story, non-bioligical).
In Action Comics #232, we met Johnny Kirk, a super-powered young man who for a brief period of time became Superman's son. Kirk sacrificed his superpowers when he learned that Superman was losing his. And so Superman was quite moved when he dropped the kid off at an orphanage:
2. Who was the Black Knight?
The Black Knight was actually Perry White. In Superman #124, the Man of Steel discovers that he's vulnerable to a sword wielded by a knight in dark armor. But it all turns out to be a trick to catch a mobster.
3. When Superman wants to return to Earth from Mr Mxyzptlk's alternate dimension, what does he say?
In Action Comics #273, Mr Mxyzptlk tries the obvious:
But it doesn't work; what Superman actually says is "Le-Lak", which of course is Kal-El backwards.
4. By what two names was Lex Luthor's bride known as in the Silver Age?
In her first appearance in Superman #167, Lex Luthor's eventual wife was known as Tharla, but in all subsequent appearances she is referred to as Ardora.
5. At what address did Clark Kent live?
Superman lived in an apartment building at 344 Clinton Street in Metropolis.
Both Dan M and Michael Rebain got 2-1/2 answers right.