Mummy?

In a review of The Eye of the Storm today, Manohla Dargis writes:

Mother or “Mummy,” as Dorothy calls her — using a humorous pronunciation that invokes the image of Boris Karloff staggering about in ragged bandages — may be fading.

I'm lost. Is the normal pronunciation of "mummy your mother" different from "mummy the dead Egyptian"? Because mine are identical. And all the jokes in movies or tv shows I've ever seen hinge on that identicalness.

Edited to add: Some people at work suggested what she meant was that simply saying "Mummy" was the funny bit - 'pronunciation' clearly not the word she wanted. "using a humorous word that..." one guy suggested. Maybe so. At least that makes sense, though it does scream of US-centricity.