This sketch animates a ghost! It uses the cos() function to make the ghost go left and right, and it uses an array to hold previous values to make the tail.
Click here to edit this code in the p5.js editor.

This is part of p5 spooky sketches printout I made for CC Fest in 2019. That printout contains a bunch of Halloween-themed examples of drawing and image manipulation. Feel free to use it on your own or in a classroom!