I recommend first watching it with you eyes closed and after that seeing how you can manipulate your perception. It was easy to hear “brain needle” with my eyes closed.
"Brain" and "green" are so similar that mistaking one for the other is not interesting. The really interesting pair is "storm" and "needle" — they seem wildly different.
I think what's going on is that the "ee" vowel sound and the hissing sound of an "s" both have a lot of high frequencies. It might be that an "ee" from a high-pitched speaker sounds similar to an "s" from a lower-pitched speaker, so the interpretation depends on what you infer the speaker's vocal frequency range to be.
And then when you notice that "needle" and "needo" sound almost the same, the "o" in "storm" is not that much of a stretch. "eedle" ~= "eeto" ~= "sto".
Edit: kind of think this is to do with the n at the start of needle being implicit as you already get the n sound at the end of green and brain. I think if you register another n the remaining sound sounds most like eedle and if you don't the remaining sound sounds most like storm... Or I may have listened to this too many times
... or at least that was true until now; I've just retried it again, and I've lost the ability to hear the "-storm" ending. I can hear "green needle" or "brain needle", but no "storm.
Instead of Green Needle I am hearing a weird backwards sounding sound.
Deep in the comments, someone posted this:
> If you slow down the audio/video to about 25% speed, you'll notice that the sound for 'needle' begins a fraction earlier than 'storm'. This is because the 's'-sound (in storm) actually begins in the 'ee'-gap of 'needle'. The 't'-sound of 'storm' atches with the 'dl'-sound of 'needle'. The whooshing sound during the 'ee'-gap of the 'needle' sound is heard by our brains as an 's'-sound and - since the brain is already primed for 'storm' - we hear the rest accordingly.
The toy is supposed to be saying Brainstorm: https://ben10.fandom.com/wiki/Brainstorm