Lionel Luthor gives Johnathan Kent his business card and the telephone area code number starts with 121. Other than 555 being Hollywood, 121 does not exist in any state nor does it belong to Kansas.
The axe can't be broken to pieces like a vase. And that refers to every episode, where Clark is hit with something.
Clark Kent's DNA would naturally be different to Pete Ross's, as they are of different ethnicity & this would be obvious when the DNA analysis was carried out, thus the lab would want to know why they had the wrong DNA sample.
Chloe and Rachel believe that Clark could be Lucas Luthor. However, in Prodigal (2003) establishes Lucas as being 18, whereas Clark is 15. So, Lucas Luthor would be 2-3 years older than Clark Kent.