So for the call for Pokemon system are their certain pokemon that have a guarantee to call after using the orb and getting them low? Like how their used to be Hordes that always showed up for that one stat.
Edit: nvm you just answered lol. So basically we can Ev train off a common mon to get what we need. Slower but eh i can do that.
I'll answer this some anyway just to get the information I know out there regarding this mechanic. I do not claim to be an expert on the topic, though, so there are likely things I don't understand.
First off, from what I've seen every Pokemon you'll normally encounter in the wild can call for help when it's weakened. Adrenaline Orbs increase the frequency of calls and last the entire battle.
Most Pokemon will call more of their species. There are some exceptions, however. The biggest exception is babies. Baby Pokemon tend to be capable of calling for the evolved form. An Elekid can call in Electabuzz, for example. In some areas, Carbink might end up calling in a Sableye (who will then proceed to attack the Carbink because yummy gems).
Happiny and Chansey appear to be directly linked to babies. I'm under the impression you won't encounter either of these through a normal encounter, but pretty much any baby Pokemon has a chance to summon one of them, depending on where you are. (Riolu in the postgame call Chansey, for example, while you'll usually have Happiny).
Happiny do not appear to call for help, so I'm assuming Chansey behave the same way. This means a couple of things... Firstly, if you're chaining an HA Happiny/Chansey, you'll need to KO any that spawn without the HA, or you'll break your chain because it won't call for more. You'll need to hope the other Pokemon summons another in later. Secondly, it means you can't farm level 50+ Chansey through this mechanic for experience.....
Common, weak Pokemon seem more likely to call for help and to succeed. My previous test with the meh results was related to Munchlax, while the Caterpie test was far better in regards to call and success rates.
Pokemon from the Island Scan mechanic are, as far as I'm aware, incapable of calling for help. This means unless Island Scan Pokemon can naturally have their HA, we may not be able to get them with their HA due to an inability to chain.
I think that about sums up my current knowledge of the mechanic.
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Edit: In response to the above post, I dunno why I didn't look to the text dumps to check for information regarding the potential of the Plaza. The fact there's a shop that can boost a stat to max is very nice even if it's once a day. Question is how hard will it be to get said shop.
I can say with absolute certainly the EV reducing berries are around and still reduce by 10 points, as per an earlier post of mine.
Those level up meals will also be a big deal unless we stumble upon something good to farm for EXP besides the E4...
Edit2: Also Incense is still around, though strangely they have varying prices ranging from 2k to 11k instead of the standard 9.6k now lol. I haven't actually tested breeding a pokemon that normally uses incense for babies though...