Even Wilhelt sacrifices its army to draw you cards
Dogmeat, Ever Loyal Interceptor, Shadow's Hound Isamaru, Hound of Konda K-9, Mark I Karvanista, Loyal Lupari Kroxa and Kunoros Kunoros, Hound of Athreos Lockjaw, Slobbering Teleporter Lucky the Pizza Dog Mowu, Loyal Companion Pako, Arcane Retriever Phelia, Exuberant Shepherd Rex, Cyber-Hound Rin and Seri, Inseparable Tesak, Judith's Hellhound Yoshimaru, Ever Faithful
(Okay, technically, red and white together can do this too.) Black also will do triggered or activated effects that repeatedly drain the player, usually for 1
Switching out your Pokemon will turn the Active Pokemon into a Benched one and since Special Effects can only affect Active Pokemon, then you heal their status effect
This is a pretty severe limitation that can keep your opponent from building up a proper team
Up to this point, there seems to be two different versions of Discover combo