The theory was proposed and it was anointed 'Planet X' when Pluto was the 9th planet, with X as the Roman numeral for 10. Now it's a play on 'X' being somethin

The theory was proposed and it was anointed 'Planet X' when Pluto was the 9th planet, with X as the Roman numeral for 10. Now it's a play on 'X' being something unknown. Nothing to get annoyed about.