Thankee. You shoulda seen some of my combos earlier in the day. Unfortunately I don't think anyone saw them : /. Gimps on spacies can be cool but i had like a 70% combo on roy on Yoshi's Island earlier. With pika. It was sexy.
Aaaaanyways, pika v ness. I haven't had too much trouble in this matchup usually, but ness can have some interesting tactical threats. The only real ness experience I've had is against N.OW, a ness player from western new york, and artery clogger (crewmate)'s alt ness. Ness has decent aerial pressure, fair covers a lot of pika's approaches, dair can make pika weary of trying to uair you, and bair is a pretty good punish if pika is caught lagging or not being ready for it when approaching. Ness can do sooome shield pressure on pika, but it's honestly not that intimidating. He has like fair->jab->grab maybe, but ness's grab range is about as bad as pika's so he has to work for them and it's often not difficult to punish him if you expect him to go for a grab.
On pika's side in the matchup, you have more that's imo scary. Jolts are still effective, as ness's first jump is kinda slow, he doesn't have a whole lot of aerial mobility to get around them, and he doesn't have much to punish with out of shield if he shields it, and doesn't really have anything that tinks with it. You've got a relatively solid defense game as ness has like 2 approach options. You can dash dance around his aerial approaches and go for grabs/usmashes, and you can shield his dashattacks and usually punish his lag or at least get away before he can follow up. Ness's upB can be a big liability. If pika gets him off the edge and forces him to upB, pika can usually jump out and steal the jolt while still having enough room to recover with quick attack, so ness then just falls to his death.
As far as comboing goes, both of them don't really have good combos on the other. Pika can get like rising uair -> nair or double jump dair on ness, and a few other simple ones. Ness doesn't have much means of getting out of them besides nair and fair, his double jump starts out a little slow and is easy to catch. Pika can get out of most of ness's stuff i've found if you DI right, so the worst he can do is like dair->bair. Killing-wise, they both have their threats. Ness's bthrow kills at like 120% from the middle of final destination iirc, bair and fsmash and uair can also kill fairly early. Ness can't do a whole lot to edgeguard pika. Pika has usmash (->thunder) of course, and his aerials can get ness off the side where you either screw up his upB recovery or just ledgehog and force him to get to the stage then hop up and punish him in his lag.
What ness does have going for him is gay counterpicks though, at least from my experience. Corneria can be dumb, as whenever ness starts getting close to kill range he can try to go to the blasters on the left side and absorb all the laser damage to get back to 0%. Green greens can also be kinda dumb, because although it has a short ceiling, the stage design makes it pretty easy for ness to camp. Pikachu has limited approach options, as you usually have to jump over the blocks and there's not much room at all on the side platforms to maneauver around. Blocks and the height of the two platforms in mid make pika's jolts effectively useless for approach or camping purposes, so ness is free to camp somewhere, punish pika's limited approach options, then run away and camp again. Pika's alright at chasing, yes, but all ness has to do is hit you with something that has decent stun. Also, ness backthrow kills at super low percents on that stage.
So i'd say advantage pika on all neutrals and some cps, slight advantage ness on some cps.