How do I make a sprite stick to solid objects (i.e. a wall)?

Specifically, I'm wondering how I could go about making a sprite stick to solid objects and circle around them (or follow them if it's a wall). As an example, something like youtube.com/watch the fire enemies at 2:22 is what I'd like to code in.

Any advice on what the best behaviors/whatever to use would be fantastic - thank you in advance!

considering that the shape of the objects is not always square, i would just set a bunch of triggers to change the direction of the object that's is moving.

of course, you can set the triggers invisible so they don't show up in game.