Simple Crab Costume Diy . Easy octopus cardboard costume for kids. To form the jaws of the. Coolest Hermit Crab Costume Crab costume, Lobster costume, Hermit crab from www.pinterest.com Diy lobster halloween costume made with a hoodie, felt, pipe cleaners and hot glue. Measure and score a 20” x 30” rectangular piece of cardboard (s1) using a ruler (t3) and pencil (t4). The wire should be no longer than about 6 to 8 inches to avoid injury to others when wearing the costume.