Here is how to get the It's A Me Grow! achievement in Raze 3:
This achievement can be unlocked on the level Nightfall. (level 12 human campaign) I'm not sure if it can be unlocked on any Overgrown map but this is just the one I got it on.
Step-by-Step Walkthrough
1.) Starting from the start (the furthest left platform in the middle) double jump up to the yellow top platform with the WC-461E on the side.
2.) At the right end of the platform double jump straight right. This may take a few tries as you might think you need to go further than you actually do, don't sweat it. You can jump from a little inside the edge and still get it.
3.) You will hit a box (a ? box like the originals from Mario) and you will grow and get the achievement!
If you're playing to play I wouldn't get it as the bigger version of you reduces your accuracy pretty greatly.
