Can I evolve the Cleffa from Obsidian Flames into Clefairy?
No. Cleffa doesn't say that it can evolve into Clefairy, and Clefairy doesn't say that it evolves from Cleffa.
Source: Obsidian Flames FAQ; TPCi Rules Team (2023-08-10)
If I use Greninja's "Water Shuriken" ability first and then evolve to Greninja BREAK on the same turn, would I be able to use its "Water Shuriken" ability again?
No, you cannot. Even though Greninja evolved into Greninja BREAK and retains the Abilities of its previous evolution, it still remembers that it has already used up its once-per-turn Water Shuriken ability for that turn.
Source: TPCi Rules Team (2016-02-11)
Can I evolve to a BREAK Pokemon while it is on the bench?
Yes. If follows the normal rules of Evolution.
Source: BREAKthrough FAQ (2015-11-19), TPCi Rules Team (2015-11-19)
Can you use Devolution Spray or Golurk's "Devolution Punch" attack against a Mega Pokemon, and if so what happens to the Mega Pokemon?
Mega Pokemon are evolved Pokemon, so the Mega Pokemon card is removed, but the underlying Pokemon and all other cards attached stay in play (unless the Pokemon is KO'd, of course).
Source: XY FAQ (2014-02-06), TPCi Rules Team (2014-02-06)
Evolution effects may take place on the first turn of the game, unless specifically stated on the card. This will affect Trainer cards, Poké-Powers, and effects of attacks. In the past, it was ruled that such an effect would have to state "This may be used on the first turn of the game." The correct usage is the card would have to specifically state "This may not be used on the first turn of the game."
Source: PUI Rules Team (2004-07-22), PUI Rules Update (2004-07-30)
A guiding rule for evolving Pokémon... If it's not in play at the start of that player's turn, it can't be evolved normally. And effects that say "this counts as evolving the Pokémon" count against being able to evolve a Pokémon normally afterward. So, you can use Wally's Training after evolving normally, but you can't use Wally's Training then evolve.
Source: PUI Rules Team (2003-10-30)
What does "This counts as evolving that Pokémon" mean, in game terms?
It counts towards the one evolution per turn for that Pokémon (with exceptions for Trainers and Pokémon Powers that break that rule) and removes Special Conditions on that Pokémon.
Source: PUI Rules Team (2003-09-26)
Certain attacks & powers (like Erika's Clefairy's Lunar Power attack, Koga's Kakuna's Emerge Pokémon Power, or TR Magikarp's Rapid Evolution attack), can break the standard "can't evolve turn 1 or the turn it was played" rule. You CAN play them on the first turn and you can sometimes even choose a Pokémon on your Bench that you just played this turn. To make it easier to understand, the standard evolution rules ("can't evolve turn 1 or the turn it was played") deal with the standard means of evolving; meaning taking the next Stage Pokémon from your hand and placing it on a Pokémon. Since these attacks and powers have you take a card from your deck and place it, they are NOT stopped by the standard evolution limits. This also falls under the term "played". Aerodactyl's Pokémon Power "Prehistoric Power" says No more Evolution cards can be played. The above attacks and powers would NOT be affected by this as those cards are not "played" (meaning played from your hand).
Source: WotC Chat (2000-11-30)
You ruled that Team Rocket's Magikarp's Rapid Evolution can be used the turn those Pokémon come into play [Ed.Note: see also "Rapid Evolution" (Jul 13, 2000 WotC Chat Announcements)]. Does that mean that if I had played TR Magikarp down on the first turn of the game, I could evolve him (I know that this is not possible, i.e., I cannot get 3 [W] Energy on Magikarp but if we ignore this limitation) ... would it be possible since Rapid Evolution ignores the normal evolution rule?
Yes, *if* you could get three water energy on Team Rocket Magikarp.
Source: WotC Chat (2000-07-20)
In the Team Rocket set does a Stage 2 Dark Pokémon have to evolve from a Dark Pokémon or can I put it on a plain one?
It has to evolve from a Dark Stage 1 Pokémon (unless you use Breeder of course).
Source: WotC Chat (2000-05-18)