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.