All-Star Superman/Funny

"Lex Luthor: (to Clark, who's taking notes) The inimitable Lex Luthor opened the floor and shook hands with a baboon in a Superman suit... Next panel... Lex: (shaking a baboon's hand) Evening, Leopold. Leopold: Raark."
 * The issue where Clark visits Luthor in prison, especially:


 * The fact that the Fortress of Solitude has a little welcome mat on the front door.
 * With a key hidden under it.
 * Possibly a Mythology Gag, referring to the giant "airline marker" key to the giant door back in the Silver Age continuity.