...starting with a Porygon2.
If I'm correct, Conversion will switch between Ghost and Normal predictably, meaning it may have a use, especially when allowing P2 to use both aspects of Curse. Recover recovers self-damage from Ghost Curse, while Normal Curse pumps up P2's (sometimes-STAB) Shadow Ball. IMO, this is the best (probably only) useful use of Conversion.
It looks good (meaning doesn't suck) on paper, but how would it do in battle? (BTW, I'm aware that Curse PP may be a problem.)
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I'm a closet Pokémon fan -- all evidence I like Pokémon is locked away in my closet.