I'm in North America, and if you listen, you will clearly hear him say "Hey!" Ok, so maybe it is a baby cry. But it sounds too much like "Hey!" to be so. Maybe he's saying "Wah!" I don't know, but whatever it is, it's annoying. It's good that Baby Mario didn't pop up in Yoshi's Story, but Yoshi's constant humming to keep himself "happy" was enough to make it even worse than Baby Mario.
If all I had to do was stay happy to get back some lame tree, I wouldn't be humming some tune the entire way. I wouldn't hum as I do everything either. I'd just walk on through, smack the enemies out of my way, then beat Baby Bowser, the end, chapter over.
btw, in a little preview Nintendo Power once had for the original Yoshi's Island, they taunted Baby Bowser by saying something along the lines of "does Bowsie want his blanket?" In my opinion, Bowsie is a better name than Baby Bowser. It would also irritate him more if we called him that.
May Yoshi live long and prosper...
Oh, and may PenguinWizard have the same treatment.