The_Dragon, it's not that we don't want to be open minded, it's just that we'd like to determine exactly what's happening before we say anything for sure. The Dair glitch you mentioned is certainly real, and there's even video evidence with Toon Link:
http://www.youtube.com/watch?v=BnRmDoJm0VI
We're not trying to tear apart the OP, it's just that in Brawl, there are several different things that create upwards momentum that not everyone might be familiar with. I've tried recreating this as Squirtle as you said, Dinivan, with little success. Can you recall what stage, and specifically what area of that stage, you were at anytime this happened?
The fact that several people have noticed this says something, but it's hardly definitive, as the situations in which each of these examples happened are completely different, and the details for most are nonexistent or very sketchy.
There COULD be something here, don't get me wrong, but at the moment there's little more than hearsay to back it up. Here is every possible explanation I can think of, using known game mechanics. See if there's any you can't immediately eliminate as not responsible, then try them and see if they look similar: Mario cape during a jump, G&W Uair, footstool jump, walljump, wallhug + jump (squirtle can wall hug), Sonic's spring. I can't think of anything else, and while most of those don't seem practically responsible without you knowing it.. that's the best I can come up with, lol.
Could you detail better what you're doing to replicate it, and where (in case it's location specific) so I can attempt to recreate it better? Understand that I'm not against the idea, just doubtful.