Gameplay » Special Conditions
If the Defending Pokémon has a status change (like Poison) but an attack requires you to flip to see if the same condition is afflicted, do you still have to flip? (Eg - Weedle's Poison Sting reads "Flip a coin. If heads, the Defending Pokémon is Poisoned.")
Yes, you have to though I can understand why you would consider it redundant.
Source: WotC Chat (2000-05-11)
Gameplay » Special Conditions
In the rules it states that when a Pokémon evolves it becomes free of Poison, Sleep, Confusion, Paralysis, or anything else that may be the result of an attack. Does this mean that damage is also taken off of it when it evolves?
No.
Source: WotC Chat (2000-04-27)
Gameplay » Special Conditions
If an opponent already has Nidoking's Toxic double Poison, then next turn I use a "normal Poison" attack, does the opponent retain Toxic's double Poison condition or does it now become a single Poison condition?
It would gain a single Poison effect (the new effect replaces the old one).
Source: WotC Chat (2000-04-27)
Gameplay » Special Conditions
My opponent attacks my Active, which causes 20 damage and Poisons it. Her turn is over. Do I then have to put 1 more damage [counter] on it because it is still Poisoned?
Yes.
Source: WotC Chat (2000-02-24)
Gameplay » Special Conditions
If you use an attack that puts your opponent's Pokémon to Sleep (like Haunter's Nightmare), and the Defending Pokémon was already Asleep before you attacked, do you still have to flip a coin after the attack to see if it wakes up?
Yes, they get to flip at the end of each player's turn.
Source: WotC Chat (2000-02-10)
Gameplay » Special Conditions
Do I flip a coin to see if my Asleep Pokémon wakes up at the end of the same turn that it fell Asleep?
Yes. You also [place] Poison damage at the end of the same turn a Pokémon got Poisoned.
Source: WotC Chat (1999-09-30)