Gotta have the classic Pikachu Tail if your gonna be Pikachu. Here's one way to do it! No-sew options too!
Use our pattern or draw your own onto paper
2 squares of yellow felt or yellow fabric to match costume
Scraps of brown felt
Batting, cotton balls or something soft for stuffing
Scissors, pins, marker
Make and trace the pattern
Cut it out
Sew around the tail using 1/2 inch seam allowance
Turn right side out
Double the brown felt, trace pattern pr free hand, and cut out
Pin to tail
Top stitch the brown felt being sure to attach to the yellow felt
Top stitch around the whole tail
Don't forget the brown part of the tail is connected to the costume.
The wide yellow end is the tip.