They really are easy, I promise: the hardest part is sourcing an orange hoodie. I made these Nemo costumes by trial and error the day before Halloween while my 7-week-old baby napped, so with the benefit of my experience you can turn your family into clownfish in no time flat.
Step 1: Tools and Materials
1 orange hoodie (zip or pull-over are both fine)
1 yard white felt (more for a bigger human)
1 yard black felt
1/2 yard orange felt (I repurposed some felt pumpkin trick-or-treat bags from the 99c store)
small bag of fiberfill, styrofoam peanuts, crumpled newspaper, bits of cloth, or other light-weight poofy stuff
orange and white face paint
Hot glue & hot glue gun (or sewing machine, but we're being lazy here)
Stapler, needle & thread, or sewing machine (for more firmly attaching tail)
Rotary cutter or scissors for cutting strips
Flexible measuring tape
Step 2: Prep Hoodie
I used a seam ripper to quickly remove the big letters appliqued on the front, but the logo on the sleeve was full of annoying little fiddly bits that would have taken ages to remove, so I gave up and hot-glued a piece of orange felt over it. Easy, and nearly unnoticeable - especially in the dark. I was pleasantly surprised.
Step 3: Design Stripes
1) a narrow, even-width stripe around the face
2) a slightly thicker, even-width stripe near the tail
3) an even thicker stripe just below the pectoral fins with a flat lower side and a curved top side bulging up in the back.
The even-width strips are pretty easy to deal with. The middle stripe caused me some trouble, as human arms are't located as ventrally as clownfish pectoral fins. Due to these space constraints, I ended up having to flip the stripe curved-side down. It gave a similar effect, and nobody besides a die-hard tropical marine biologist, aquarist, or OCD 4-year-old Pixar fan will possibly notice to call you on it.
To design your stripes, lay your hoodie out and take measurements. Here are mine, for reference - I'm using an Adult Medium from Old Navy, and a Child size 4 by Osh Kosh B'gosh. If you've got tons of time, test with paper mock-ups to make sure your stripes will look good, then transfer to the felt. I was short on time, so winged it. Let's be honest: if you're looking for a no-sew costume, you're almost certainly going to be short on time and winging it too. So start with my numbers, and tweak to fit.
Adult hoodie dimensions: 40" around below the sleeves, 16" from sleeve to lower hem, 30" around the hood.
Adult hoodie stripes: 5.5" bottom stripe; center stripe 4" at chest, 5 1/2" at back, 7" max curve; 1 1/2" head stripe. 1/2" of black trim showing on each side (cut 1" strips).
Child hoodie dimensions: 28" around below sleeves, 10" sleeves to lower hem, 22" around the hood.
Child hoodie stripes: 2 1/2" bottom stripe, center stripe 2 1/4" at chest, 3 1/2" at back, 4" max curve; 1 1/4" head stripe. 1/4" of black trim showing on each side (cut 1" strips).
Step 4: Design Tail
Depending on how much time you have, modify away. The adult costume was as we were about to run out the door, so while it still has the black fin-edge (yep, that was done earlier), there's no additional orange piece - I just hand-tacked the tail to the base of the hoodie with a needle and thread. I much prefer the look of the costume using the extra piece of orange felt, and it gives much better attachment points so you can use hot glue for everything. Yay laziness.
For the child's hoodie, I folded the orange felt in half (yay symmetry!) and set the sides at 2 1/2" and 7 1/2", then just cut a straight line between the two. Figure 1/2" off the top lost to hot-gluing, as you really want this to stay on! The tail measures 3" on the short side, 7" on the long side, and about 7" in length. Again, leave about 1/2" for hot-glueing seams. You can sew this if your kid is fidgety, but the hot glue will do OK in most use cases.
Step 5: Cut Felt
Black felt: cut lots of long 1-inch strips.
White felt: cut head and tail strips. Cut mid-body strip to length at maximum width, then fold in half (to ensure symmetry). Mark back and zip endpoints, draw a smooth curve between them, then cut the curve.
Orange felt: Fold in half (to ensure symmetry) and mark length of back and zip sides. Cut between the endpoints to make a sort of squat, irregular pentagon. Cut two pieces of orange felt to make the tail itself.
Step 6: Glue Felt Strips
WARNING: hot glue is hot! Always keep a bowl of water so you can quick-cool the glue by dunking your hand when you (invariably) get some on your fingers.
Apply a bead of glue to the black felt strips, then press the white felt down onto the black, leaving the proper amount of edging visible. I used 1/4" on my child's hoodie, 1/2" on the adult's hoodie. YMMV.
Continue until all white stripes have black edging along both long sides.
Step 7: Glue It All Together
1. Glue tail together, and stuff with fiberfill (or soft/light substitute).
2. Glue tail into orange hoodie extension. Use lots of glue, as this will get bonked around a lot.
3. Glue hoodie extension/tail to bottom of hoodie; inside or outside is fine. Use lots of glue here too.
4. Glue bottom stripe around hoodie.
5. Glue head stripe around hood. Be sure to space it an inch or so away from the front edge of the hood.
6. Glue center/curved body stripe just under arms. This one is the tricky bit - since the hoodie doesn't lie flat here, you may need help getting it placed and glued. A dress form would be perfect, but a ball, a second pair of hands, or a (well-insulated) wearer will make this go.
NOTE: Be careful to glue the right side of your stripes down! I was in a hurry (surprise!) and glued the last piece upside-down, so the middle stripe of the adult hoodie has inch-thick black edges. Nobody seems to have noticed, but it still annoys me.
Step 8: Apply Facepaint, and Wear!
For bonus points, apply white face paint in big circles around your eyes, and paint the rest of your face orange to match your hoodie. Go forth and trick-or-treat.
My little fishies were a huge hit! Children squealed "look, it's Nemo!" everywhere they went, and my 3-year-old was so proud to be recognized. She loves to wear her Nemo costume to non-Halloween events, so we're getting more use out of it than I'd anticipated. It's almost practical.
If you make one of these, please share your photo in the comments! I'd love to see how it turned out, and will give a coupon for a year's Pro membership to everyone who posts a photo of their own version.