how does wobbling even happen because every time i watch a melee tournament i can never figure out how it happens
my best guess is some bug makes nana and popo pummel at different times so they just never get out of the grab?
You can desync Nana and Popo so that you can control them both independently at different times. To wobble, you grab someone with Popo (the one you're directly controlling) and pummel them once, and then you f tilt them with Nana, and then you pummel them again with Popo, and f-tilt them with Nana, etc.
They can't get released from the grab until the hitlag stops or something so they are just stuck in the grab. It's incredibly easy to execute once you know it, you just tap A at a certain rhythm.