Endless Battle Clause exists in Anything Goes, which should ban Leppa Berry+Shadow Tag+Trick.
Yet somehow, this guy managed to get it through and force an Endless Battle.
http://replay.pokemonshowdown.com/anythinggoes-188360564
Perhaps Endless Battle Clause isn't implemented properly?
---
Edit: Another Anything Goes bug, I think. I'm not sure. Correct me if I'm wrong, but, in-game, I think there is no legal way to have multiple Kyurem on your team, unless all but one are in "normal" form. If you try to use the DNA Splicers to combine a Kyurem with Reshiram/Zekrom while there is a Kyurem-Black or Kyurem-White in your party, I think it will just split the fused Kyurem into a non-fused one. This doesn't really matter too much for metagames with Species Clause, but for Anything Goes, you should ban having multiple Kyurem-B, multiple Kyurem-W, and having Kyurem-B+Kyurem-W on the same team, if this is indeed the case.
The one thing that has me scratching my head is that it might be possible to trade over a fused Kyurem from another game while having one in your party anyways. I don't know whether that works or not.