Ah I remember these from way back when, good and fun times.
Anyway, this was overall pretty nice. For being a showcase/small demo on how to craft animations, I think this is pretty competent. I really like the visual style you decdided on, more specifically all the fun textures in the background. As someone has already stated, the story is just a tad too self-explanatory and I guess you could say rather predictable, which I'll admit had me asking "Wait, that's it?" by the time the credits rolled around.
Speaking of rather confusing directional choices, I really didn't get why the little dino shed a tear when he was about to fall on the tub. The shot by itself is fine and dandy and its purpose is clear - to add a tidbit of comedic drama and buildup for the obvious growth spurt gag, it's just that little detail on the character that doesn't really make sense. He certainly seems to be just fine once he turns massive, so what made him so emotional back there?
The voice acting is redundant but admittedly pretty funny, so honestly I don't mind it. Overall it's a fairly solid little short, and as with any animated work, I applaud you for putting in the time and effort required to complete such a task - being frank, I've learned over the years just how time-consuming and demanding even the simplest of animations can be, so props to you for making it through to the end with this one and everything else you've dished out.
Godspeed!