a few nuggets of constructive criticism:
you should think about mediating the power of the ladders, cus like basically any ladder ostensibly gives you infinite jumping power
IMO the rewind should go much faster. it almost seemed like it was actually slower than the regular speed of the game
short falls didnt seem to add anything to the jump meter and it was somewhat unclear whether there was a specific threshold of how high the jump needed to be in order to do so. jumping off of crates should add a little bit at least, but i found that i gained nothing from them even when stacked up 3 high, yet two gray blocks was enough in other levels.
when pushing crates down steps, the crate would often get stuck with a considerable gap between it and the wall, which was clearly big enough to fit the pig in so that i could continue pushing, but the little guy kinda just hovered there and i was down one crate unfortunately. maybe you could allow the pig to slip in there even if it's a tiny gap. a lot of platformers allow for some wiggle room to avoid this kind of thing
IMO the springboards shouldnt automatically expend your energy. it doesnt trigger when you land or when you use your basic jump, so it doesnt make a ton of sense to force it in this situation
the level with 4 buttons in midair next to each other had a small glitch where i could stay on top of the box after it disappeared so long as i let go of the down key before hitting the button, which allowed me to press all four buttons at once instead of having to bounce back up or climb the ladder.
when crates are stacked, i can only push the top one. i think it'd make more sense to have them move slower when weighed down, or just allow all of them to be pushed regularly. it does make sense for multiple adjacent boxes to be immobile, but when they are stacked friction doesn't come into play in the same ways.
maybe increase the move speed. it works earlier on when the puzzles are simple, but once you have to backtrack and perform actions multiple times, it becomes a little tedious to wait for the pig to cross the screen.
covering lava with crates works puzzle wise but doesnt make any sense when you consider that they seem to be made of wood. you could think about introducing wooden ones as platforms on top of spikes or water or various room temperature hazards, and then maybe bring in metal or stone ones which can be placed on lava later on.
havent finished yet, gotta run, but ill check back in and message you if i have anything else for u
good job!

I get stuck into the springs at the bottom of the last level, which is very frustrating because I had really enjoyed the game so far. I'm running it with the last stable version of Chrome on Ubuntu 14.04. I hope you can do something about this :) Very good game !

Cute little game. Themed for kids and you did a good job.

But why does the pig have a spring???

The simplicity of the start slowly morphs into a great puzzle for truly everyone. Good job! One of the best Newgrounds games I've seen!