The 69-year-old TV star sported yellow eyes as she helped Jay Leno get into the Halloween sprit.
“I have Halloween eyes. They’re contact lenses,” she reassured the shocked host.
“I love Halloween. I love transformation. At Halloween you can transform something into something else.”
Stewart showed off a banquet of green slime, beef tongue, chicken feet and pigs’ trotters as a bemused Leno attempted to take it all in.
The business magnate confessed she gets so enthusiastic about the ghoulish holiday she puts her French bulldogs in fancy dress.
She also showed off photos of two of her favourite fancy dress outfits – a Little Bo Peep costume which she wore as a child, and a skimpy Wonderwoman outfit she wore in later life.
“I made that one,” she said proudly.