I remember a movie about a woman who is terrorized by small little
creatures hiding behind the furnace in the basement and a part where she writes a message on the bathroom mirror.Could this be the same movie?
Possibly -- if your memory/detail recall is fuzzy, as I don't think there was any writing a message on a mirror (though there was a shower/bathroom scene).
The three creatures in this movie were seldom seen but looked like aliens or run-over prunes or shrivelled monkeys and were about 14-22 inches tall. They could disappear in the blink of an eye and were never fully seen. They could certainly be touched and could grab you, and had some physical limitations due to their size, but could slip away and escape almost as if they had extradimensional properties. Light (especially direct light) seemed to terrify or harm them immensely.
Their access to the house was through an ash pit (or ash dump), which has an iron door in the brick hearth floor of a fireplace -- this one evidently in the basement or maybe at best on the first floor -- in a previously locked-off and very dank 'library.' The fireplace in the library had also been bricked over and reinforced with steel bars, but had been reopened at the request of the wife. The room was dark an musty like a basement and there was iron and a fireplace involved, but it wasn't technically a furnace.
The classic line from the movie was iwhisperings in the dark with weird echoes, 'Sally, We want you!" and several attempts at abduction and making their presence known to the hapless young wife.
And 'cause' never was the reason for the evening
of the tropic of Sir Galahad.