If an opponent's evolved Pokemon is Knocked Out while Gengar is Active, does the "Catastrophe" Poke-BODY put all of the evolution stage cards and Basic Pokemon card in the Lost Zone, or just the highest stage Evolution card?
The evolved Pokemon and any of its pre-evolved stages and Lv.X cards go to the Lost Zone, and all attached Energy, Tools, etc. go to the Discard Pile.
Source: Triumphant FAQ (2010-11-04), PUI Rules Team (2010-11-04)
If I use an attack that Knocks Out a defending Gengar with the "Castastrophe" Poke-BODY, but it also knocks itself out, does the attacking Pokemon go to the Lost Zone, or is "Catastrophe" no longer in effect when Gengar is KO'd?
Since both Pokemon are KO'd at the same time, Gengar's Catastrophe Poke-BODY is still working at the point when Knock Outs are evaluated. So the attacking Pokemon would go to the Lost Zone.
Source: Triumphant FAQ (2010-11-04), PUI Rules Team (2010-11-04)
If my Active Pokemon does an attack that Knocks Out an opponent's Pokemon, but also switches my Active Pokemon to the Bench, would the Knocked Out Pokemon go to the Lost Zone if I bring up Gengar with the "Castastrophe" Poke-BODY?
Yes. Gengar is active at the end of the attack when Knock Out conditions are evaluated.
Source: Triumphant FAQ (2010-11-04), PUI Rules Team (2010-11-04)