Me either really ;~;
I'm hoping other IC mains can find something to do with it. So far all I've found is having Nana do an extended range grab, Nana spinning back from where she teleported to Popo, or some kind of interesting hopefully useful desync setup. So yeah... Hopefully someone finds something cool with it...
Edit: to help along people explore this tech and it's possibilities, I'll post all I know about it so that it's easier to play or experiment with.
It can only trigger on Popo's Dair, as any other normal or special will have side B come out like normal. Sometimes when it's performed wrong, Nana will blink out of the picture for a second, but be back exactly where she was instead of forward. And it seems to give the IC's some sort of longer range on their syncronization as after they've separated, you can dash in the opposite direction of Nana, and then Dash Dance and Nana will mimic the dash dance from that far distance when she would normally just return to Popo. To make Nana spin back to where you are, you actually have to continue holding Side B, as any input will have her run back to you without doing the spin. It can set up for some interesting desyncs as it puts the IC's in a desynced position that's otherwise difficult to attain, with you controlling desynced Popo while Nana travels back to him from far in front of him.
I'll keep looking for applications for it, and I hope you guys do the same. If you have any questions I'll be happy to answer.
Double Edit: I just got a really weird visual glitch to happen that I desperately want to recreate. Basically When Nana teleported I had Popo dash in the opposite direction, and it caused Nana to Blink short distances closer and closer to Popo. Really weird, but neat.
Triple Edit: Okay, OKAY, I think I found an application! If you can time it well, you C stick smash right as nana teleports, and she will fly forward out of the teleport doing a smash. I've only got it to happen once but it was insane. She slides a bit further than WD distance while performing the smash.
God damnit, this is really difficult. I don't know how I caused it the first time. I'm recording all of my lab time now so when these weird techs occur I can record them. Here's my almost recreation. I got her to slide, but not smash.
I should probably give up the ghost on this one. As neat as it is, it's horrendously difficult, as I've only had it occur successfully once, and gotten the flub slide twice in about a half hour of trying. I might investigate further later, but for now I'm tapped out.
Literally five second later edit: I did it again! It is inputting Dsmash on the Cstick right as Nana teleports! I don't know how consistently it's possible but I'll try to get a recording of this damn thing!
Final Edit: Success! I'm guessing it's a one frame deal, but I've done it a couple times, and it's great! The tech is now useful! I don't have any editing software so I'll just point to it being performed near the end around 3:35 and without further ado give you, The Nana Torpedo! After more testing, it's actually not that hard to do consistently! I changed my control scheme a bit to do it easier, so I now have Right Trigger set to special as it lets me use my right thumb to flick the C stick down easier, but it's really plausible with standard controls as well.