Place the hat on a flat surface with the bill of the hat laying flat. Use a marker to outline the bill on a piece of craft foam. Cut the foam with a pair of scissors. Fold the bill firmly in half making a point at the front for the beak. Use a hot-glue gun to attach the foam to the top of the bill of the hat. Starting at the back of the hat secure the feather boa to the hat with hot glue. Circle the boa around the hat adding more glue about every 3-4 inches. Add just enough boa (about 3 feet) to cover the bottom two thirds of the hat, leaving a circle at the top uncovered.
Make a party hat by rolling a piece of metallic paper into a cone. Add hot glue to secure the edge and then cut the bottom to remove the excess. Glue the party hat to the ball cap at the uncovered circle. Add a gift bow or other embellishment to the top of the party hat.
Lay a t-shirt on a flat surface. Insert parchment paper between the front and back layers of the t-shirt. Starting at the shoulders, attach the feather boa to the front of the t-shirt with hot glue. Zigzag the boa back and forth over the front of the shirt moving toward the bottom, adding glue every 3-4 inches. Place the lines of boa just far enough apart for the feathers to fill in the gaps. When the glue has cooled, remove the parchment paper.
Make a party fowl sign on a piece of foam core or painted cardboard about 12” wide and 6” tall. Poke holes in the corners with an awl or screwdriver. Attach a string of beads to the sign with twist-ties wrapped around the beads and poked through the hole. Tape the twist-ties down on the back side of the sign. Alternatively, use ribbon and tie it through the holes. Add accessories like a party horn.