Notably, these characters are not encoded in the English games. Apparently they're 0xBF (Á) and 0xC9 (Í), which has no documented equivalent in the English Generation II games; in the English Generation I games, 0xBF encodes 'v.
So, I have a few questions. If you trade these Pokémon to non-Spanish games, how does it display in each language and generation? (I would speculate that FALCÁN is displayed as FALC'vN in English Generation I.) And now that Generation II is available on Virtual Console, what happens if you trade Voltorb back to Generation I and send it through Poké Transporter?
It's worth noting that a similar quirk occurred in Generation III and IV, where diacritic characters from in-game trades got converted to Japanese characters by Pal Park.