Ghosts can be scary. I have to admit I never saw one, so I won't chime in with my comments on the question if they exist or not.
However, here is a double knitted potholder showing a ghost. Remember, it is knitted. It is not real.
This is a charted pattern. It includes a short introduction to double knitting. If you have never used the technique before, you may find it helpful to watch tutorials. The potholder has a crochet border around and a hanging loop, which requires knowledge of basic crochet stitches. If you don’t want to do that, there is nothing lost if you leave it off.
Difficulty level: intermediate (double knitting, working from charts, basic crochet stitches)
Yarn: Steinbach Capri (100% cotton, 125m/50g; 137yds/1.76oz), 1 ball of each color. Sample used 58m (63yds) of each color.
Needles: 2.5mm/US 1 1/2. If you want to crochet a border, you also need a hook in size 3.75mm (F).
Notions: yarn needle
Gauge: 22 stitches/33 rows in doubleknit stockinette = 10cm (4in)