Like many kids today, mine love Minecraft. My son wanted to be a creeper this year and we were up for the challenge. We found some unused cardboard boxes at the local home depot and built each body part from the pieces (head, body, telescoping part of body, and 4 feet).
The biggest challenge was making it possible for him to climb stairs and figuring out how to raise and lower the body. We ended up using straps on the inside so he can lift it while walking or climbing and then set it down. We had a local printer print sheets of creeper paper right down to the creeeper toes and we adhered them to the cardboard. He went to a local festival and it was so clear who was a Minecraft fan. Many kids requested a photo with the lifesize creeper!