halloween costumes.. easy, cheap, handmade?

[My Sweet Blessings]

cheap is very important, prefer handmade, but will buy if it's the cheapest.. .. .. I normally can persuade my boys to dress how I want them to, but that has come to an end. One wants to be Sonic and the other blue angry birds (space version). I need ideas on how to throw this together. it doesn't have to be perfect. I prefer it to not be hot (it's hot down here and they will sweat like crazy), and something that can be worn to school, aka, not bulky or difficult to get off and on for potty trips.

Sonic.. some ideas.. fleece hat, stuff spikes with poly fill. 2 piece for body so my son can go to the potty easily. for kindergartener

Angry birds.. I have no idea. for 2nd grader.