As important as getting Thoron is in this match (which it definitely is),
/
is one of the few characters that can actually crouch, DTilt, and even Side Taunt UNDER Thoron. An Alph that is aware of this and in a position to take such actions is someone that you're going to have to catch doing a standing or aerial action (that's not blocking or properly-timed airdodging or spotdodging), including recovering, in order to reliably land Thoron. Otherwise, he'll probably DTilt towards you while Thoron's going and potentially KO you for it, especially if he's got a Purple or Red Pikmin next in line for a Smash attack. Oh, and Yellow Pikmin can survive it. As someone who plays a lot of FG Teams (followed by FG FFA, and hardly any FG 1v1 (unless it somehow happens in the FG FFA room)), catching him doing a standing or aerial action or recovering is much easier in Teams, due to having a partner that could read Alph's crouch/bait and make him stand up or be in the air long enough to land Thoron.
DTilt will get some use in this MU, due to it being one of the more reliable moves you have that can reach Alph. It's quite fast & repeatable (comes out at frame 7, ends on frame 8), making it pretty good at picking off thrown & missed Pikmin as well (even some of the ones that successfully latch on to you). If in the air, NAir is also pretty good at picking off Pikmin, since it covers a wide area around you and has very little landing lag, leading into DTilt or Jab string for more Pikmin KO-ing power.
Can Alph duck under Robin's FSmash as well? If so.... *shivers, thinking of the
/
VS
/
/
MUs*
Alph's most important Pikmin in terms of surviving your moves are Red and Yellow Pikmin. Reds survive ArcFire, and Yellows survive Thunders and Levin Sword. Of those two, Red has the higher KO power. Getting rid of those two Pikmin types are gonna be tough with your moveset. While Purple is his strongest KO-ing Pikmin, as well as probably having the best defense of them all, all of your moves will damage it, much like what you can do to Blue and fragile White Pikmin.
Would spending Thunders to ward off non-Yellow Pikmin be worth it? I'm not sure. Probably not, considering how important Thoron is for piercing through them all. ArcFires would probably be worthwhile for warding off non-Red Pikmin. Rushing him down and keeping him in the air (he can't pluck up more Pikmin there!) when he's got 1 Pikmin or even none is your best bet for controlling the match, since he'll only have his Neutral A, tilts (FTilt CAN KO at 140+%, though), and NAir when he's stuck being NOlimar/NAlph. No grabs or Side B or other aerials or Smashes when he's without Pikmin. His Up B recovery, however, will take him very far at that point, and he can NAir out of it. Of course, getting to that point is going to be a challenge, especially without Customs.
With Customs on, you'll get Fire Wall and Speed Thunder. I personally adore Gliding Elwind for the horizontal on-stage movement, OoS escape option, and extra spiking chance, but default Elwind will probably be preferred. While I may prefer Goetia for its range and suction, default Nosferatu will also probably be the preferred option. Distant Nosferatu COULD be of use for this MU, but I doubt he'll be keeping his distance from you too often like
(who is definitely one of Robin's worst MUs, alongside
, considering how capable he too is at warding off Fires and Thunders, and that he's also able to CRAWL
under Thoron) and
would, unless he's running Side 3 (Tackle Throw), in which case, going Down 2 could work.
With Customs on in teams, Thunder+ may be the better option, for your partner could help you charge it. Fire Wall will still be pretty good (and may be the preferred option, depending on how much Alph will try to get in your way), but ArcFire+ might have merit in this setting, as will default ArcFire, which could be the preferred option, considering the setups that both you and your partner can get out of it, provided Alph doesn't actively try to get in its way. Again, default Elwind will probably be preferred, but I'd still rock Gliding, even though the chance of spiking your teammate as the both of you are trying to get back to the stage sucks. Default Nosferatu will also likely be preferred.
Of course, Alph will get to run either 2212 or 2232 or 3312 or 1312 or 1112 or other such sets, whether in singles or teams. 2212, 2232, and 1312 will probably be among the more concerning sets, because Hardy Pikmin will be even harder to get rid of, and Sticky's damage is boosted with Hardy Pikmin (not per hit, but by length of time), should any of them actually cling on to you. Tackle Throw boosts his ability to wall you out, especially once he has you off-stage. Order Tackle, as many of us are likely aware, can make his Pikmin scary powerful if he's paired up with someone like
....
Speaking of off-stage, Alph's DAir can spike you pretty early at 60-80-ish%, especially if he does it with a Red or Purple Pikmin. He'll probably try it with a Yellow Pikmin to challenge your Levin aerials, which he'll also try for every other air battle if possible.
If they're at 90+%, you can expect Alphs to try to Down B super armor through your KO moves, as well as Up B around you after using all their jumps to position themselves to safety (including coming down at you with an aerial when you've whiffed something laggy while they're in the middle of their Up B).
If you're at 90+%, expect Alphs to try to organize their Pikmin lineup so that Purple or Red or Yellow Pikmin are at the front of the line, ready to Smash attack or BAir you. In low-ceiling stages or if you're at around 150-ish+%, Blue Pikmin may be a part of that lineup for the Up Throw.
If you're off-stage, they'll hound you to the ends of the stage with either Purple, Red, or Yellow Pikmin, due to how far their Up B can take them, especially when they have no Pikmin in line.
If the MU is still too frustrating for Robin to handle, perhaps a character switch is in order? Like
or
/
or
or
or
or even
/
?
I seriously do suggest
, for Nayru's Love shreds Pikmin in one go, even Reggies (aka Purples). As an Alph player, Zelda's someone I don't get to use Side B against too often for that reason, which is why I tend to lose against her when I'm Alph.
If in a team setting, hopefully you're allied with one of the aforementioned characters and not someone like
or
or even
(their default Side Bs get rekt by thrown Pikmin, especially when they're trying to recover), so it'll be easier for you to focus on Alph's partner for the majority of the battle (who we hope is not someone like
or
or another
/
), while your partner focuses on Alph himself.
As for location, definitely stages with platforms like Battlefield or Smashville or Lylat Cruise. Considering the might of the Reggie Up Smash and the Blue Pikmin Up Throw, Halberd and Delfino Plaza and possibly even Town & City may NOT be advised, due to their low ceilings.
Splooshi Splashy
. Color me impressed. That's some really great and in-depth matchup advice. Thanks and bravo! 
