Clark's name was given to him by Jonathan and Martha as it was the maiden name of Martha Kent (Martha Clark Kent). However there is no explanation as to why Lionel named him Clark Luthor and not kept in line with the "LL" motif that has gone on with most of the Luthor family members (e.g. Lachlan Luthor, Lionel Luthor, Lex Luthor, Lucas Luthor, and Lutessa Lena Luthor). It would've made more sense to name him Julian (the name Lionel planned to give his third son) or Kal.
The only colors that are visible in the other world are green, blue, and red.
In the newspaper, the story "The Blur Saves Under Scrutiny" is reported by Henya Bak. Henya Bak was an accounting clerk for "Smallville" for one season.
Lionel tells Clark about putting on an Ultraman persona, this is true on Earth-3 he was a tyrant of what was known as the Crime Syndicate and kryptonite actually made him stronger, Krypton never exploded and he was sent to Earth to rule it by force.
When Clark Kent returned from the mirror universe, Lois recognized he was the real deal, unlike Lana who couldn't tell the difference between Clark and his doppelganger Bizarro in Season Seven's "Gemini" and "Persona".