Introduction: Adventure Time! Finn Costume! Backpack (functional, With Zipper Opening) + Hat.

About: Compulsive thing-maker.

My kids love Adventure Time. They decided they wanted to be Finn and Jake for Halloween. The cartoon is pretty new and you can't find any Adventure Time stuff in stores so I had to make their costumes from scratch. Here's what I came up with for my boy's Finn costume.

Step 1: Finn's Backpack

For the backpack, find some light and dark green fabric. Felt holds it's shape best. You could also use fleece or cotton.

Cut 2 light green fabric rectangles 12 inches wide by 6 inches long. Cut 2 dark green rectangles 12 inches wide by 10 inches long. Flod these pieces and round the edges.

For the edge of the backpack: Cut one dark green strip 3 inches wide by approximately 29 inches long. Cut one light green strip 3 inches wide by approximately 20 inches long.

For the straps: Cut 2 dark green strip 5 inches wide by approximately 12 inches long (10 inches long if the backpack is for a child). Cut 2 light green strip 5 inches wide by approximately 10 inches long (8 inches long if the backpack is for a child).

Other things you'll need : One 16 inch zipper and one black button and some polyfil stuffing.

Step 2: Finn's Backpack

Sew the dark green edge strip to one of the dark green rounded rectangles 3/8 inch from the edge. Trim any excess.

Sew the light green edge strip to one of the light green rounded rectangles 3/8 inch from the edge. Trim any excess.

Pin and sew the dark green backpack piece to a 16 inch zipper. Next, pin and sew the light green fabric piece to the other side of the zipper.

Step 3: Finn's Backpack

For the straps, sew the light green fabric pieces to the dark green fabric pieces. Fold over and sew 3/8 inch from the edge. Cut ends at an angle as shown and sew one end closed. Turn the straps inside-out and stuff with polyfil. Pin edges to the backpack front 3.5 inches from the zipper on either side (3 inches for a child's backpack). Carefully try on and adjust as needed. Sew straps 1/8 inch from the edge.

Next pin the back panel on and sew 3/8 inch from the edge. Unzip and turn inside-out. Sew on the button and you're done!

Step 4: Finn's Hat

For an ADULT hat hat, cut a piece of white fleece 13 inches long and 28 inches wide. Fold and trim an angle one inch in from the unfolded edge.

For the face hole, cut an oval 3 inches from the top and 3 inches in.

For the top, cut a circle 8 inches in diameter.

For the ears, cut 4 fleece pieces 3 inches wide and 4 inches tall.


For an CHILD hat, cut a piece of white fleece 12 inches long and 26 inches wide. Fold and trim an angle one inch in from the unfolded edge.

You'll need some polyfil, cotton balls,or tiny fleece bits to stuff the ears.

For the face hole, cut an oval 2 inches from the top and 2.5 inches in.

For the top, cut a circle 7.5 inches in diameter.

For the ears, cut 4 fleece pieces 3 inches wide and 3.5 inches tall.

Step 5: Finn's Hat

Sew the back edge of the hat. Next, pin the circle on top. Sew it to the hat 3/8 inch from the edge.

With the hole in front and the seam in the back, fold your circle in half to find the midline. Mark and cut 2 slits for the ears. Keep hat inside-out and insert ears. Sew 1/8 inch from the edge. Repeat with the other ear.

Turn right side -out and fold bottom edge under once and stitch a straight line around the bottom.

Step 6: Finn's Costume

We found this aqua blue t-shirt at the dollar store and I made some simple pants with blue cotton fabric. Finish it off with white socks and black shoes and shout... WHAT TIME IS IT? ADVENTURE TIME!