So Many Me

The earliest place to unlock this achievement is in The Mine I, which is unlocked after completing the Outskirts world.

Right near the beginning of the level, after walking forwards and seeing two cinematics, a 'moon' will appear donning a super stylish monocle.

From here, simply 'block jump' up to the moon (going around the area where you can't transform), land on it, and then walk all the way round it once. At this point the achievement will unlock.

Here is a video for a visual guide:

Found on The Mine I. The moon shows up in a few other places like the end credits but this is the one you want.

Now that you know where it is, it's the simple matter of getting on top of it and walking on it.

Here is a video guide, this achievement starts at 19s in: