Is M-Lopunny that viable in triples though? I would imagine the opportunity cost of being your mega, and prevalence of talonflame and intimidate users as well as its frailty and inability to hold a focus sash would severely hold back it's potential?
Quick Guard is everywhere in Triples and makes it extremely difficult to use Talonflame as a reliable attacker -the only team I've got Talonflame on I actually use it to set priority Tailwind and then ideally die ASAP- while Ghosts are
also common because their immunity to Fake Out is invaluable. Mega Lopunny messes with that, which is priceless.
Intimidate isn't really that common in my experience, barring the odd all-Intimidate team. It's too easy to ignore it with Special attackers or punish it with Defiant/Competitive (And unlike in Singles or even Doubles it's essentially impossible to simply make a good choice in timing to avoid triggering Defiant), and regardless Ghosts are so Physically fragile that even at -1 Mega Lopunny can get in a lot of work against most Ghosts. Mega Lopunny's epic Speed is also useful for getting the edge without having to worry about Quick Guard, and in fact it's so fast that if if you're not looking at Prankster Quick Guard it can probably Fake Out
the Quick Guarder, possibly even on the turn it Mega Evolves.
I think trick room can be much more powerful than people give it credit and I think triples may be it's best format- for example using sableye with a mental herb/ aromatiss support, it is impossible to stop trick room being set up without a scrappy fake out from kanga or Lopunny, which can be easily quick guarded no? (Musketeers, talonflame which works well in tr because oF priority etc)
Quick Guard is +3 priority. Fake Out is +3 priority. If your Quick Guarder is Hitmontop, which is by far the most popular choice in Triples, then both of those Pokemon absolutely
can Fake Out right through your pathetic attempt at a Quick Guard. Furthermore, in a Trick Room team your Pokemon are probably all going to be as slow as possible (Special exception: Talonflame is popular in Trick Room because of its reliance on priority, though even then it usually runs bulky) so if for some bizarre reason you brought Keldeo into Trick Room (??) odds are that you've done everything you can to drag down its Speed, in which case it can
still be Fake Out-ed through in spite of having higher base Speed than Kangaskhan and Lopunny.
I don't think people underestimate Trick Room at all. It's very popular on the ladder, much more popular than the even more obnoxious Terracott.
Ie a lead of Sableye/ any ghost with a focus sash, aromatisse and talonflame/ bulky truck room hitter, is extremely hard to stop
Those three in specific as a lead cannot be Taunted and can be tricky to Fake Out -but they're a
lot easier to simply rip up with basic offensive pressure.
Edit: on Gengar, from memory (on phone so can't do calcs, doesn't it miss the ohko on most specially bulky setters? (When taunt isn't an option due to aroma veil)
This is Triples, you shouldn't be assuming it's operating alone. Furthermore, barring what I personally call "stealth Trick Room" it's usually obvious that A: it's Trick Room and B: which Pokemon they lead with is the setter. Ganging up is absolutely viable. Not only that, but Trick Room teams rarely carry Wide Guard, or carry it but don't use it first turn because they're expecting Fake Out and want to block it, so spread moves can really,
really mess up an attempt to set Trick Room, possibly costing them half their team to no benefit.