SORRY FOR DOUBLE POST
My summary on the matchup
This matchup isn't to complicated. We all fear the IC almighty grab, but to what extent? Their puny grab range, that any decent player can outspace them. On the ground, simply yo-yo's can help keep Ness in the clear while the IC approach with the squall. Use simple ground attacks, such as jabs and tilts, since the IC will punish any messups with a grab. PKF should only be used when your SURE you can get away with it.
(alternatively, those skilled with the mighty arts of PK jump and Firebounding, can use those instead)
Punish whiffed smashes with a grab. Make you use Ness dash grab, since Ness will slide when he grabs his prey, just enough time for Nana to be killed with a backthrow (with a dash grab, Popo will barely have enough time to react) He you grab popo, quickly use a backthrow, less you want Nana to attack you. Seriously killing the IC is a piece of cake with backthrow. Popo on his own is relatively light, and Nana has really stupid AI and will DI in the WRONG direction, killing her earrrrrrrrrrly. (75% early!) Once she's gone, deal with the lone Popo, and keep him at bay with an aerial ****. When the time comes, you can backthrow for hs death.
In the air, you can combo with aerials to also keep the IC's at bay. The squall hammer is annoying, but escaping it's wrath and leading into a punish is really a work of art. Anticipate and lead into a PKT2 on a whiffed aerial squall. Once the IC are off the ledge, you can use PK Flash to kill them on getting back on the stage with such a predictable recovery. (If Nana is gone, popo is screwed) or you can go and chase them yourselves and spike them with dair.
*Ness is lucky by that fact that he can't get forward throwed CG. They have to use the other methods.
On the flipside, IC have plenty of tools to kill you. Getting grabbed by a GOOD IC is scary. They the average down throw CG, and can get you to the ledge to attempt to spike you (with Nana) The spike usually isn't strong enough to kill you at 0%, by they will attempt to gimp PKT with an ice block. You are spiked, used your PKT2 ASAP, or you will die. If your they hit you, double jump (you should save it) if not, your screwed. Squall hammer, can stop your ground approaches too. Getting grabbed and rapped by blizzard is not fun either.
IC are indeed a tough opponent, but they are not impossible. 5-5