Unexpected Guests

Every third Tuesday, Grandmother locks herself in the basement to do laundry.
My mom told me that Grandmother has always done this, even when Mom was little.
Everyone else just accepts this as one of Grandmother's quirks, and have grown tired of me wondering why.
The only one who doesn't pat my head and tell me to go play like I'm a little kid is Grandfather.
He's even worse.
Grandfather gets this twinkle in his eye, lifts a finger to his lips, and says he's been sworn to secrecy.
Then he has the nerve to wink.
So today, I decided to get to the bottom of this mystery by hiding in the basement.
When I hear Grandmother at the top of the stairs, I make sure I'm hidden behind the boxes of Christmas decorations. I can see the washer and dryer from here, but hopefully Grandmother won't turn at just the right angle to see me.
When Grandmother comes down the stairs, I frown a little as she starts sorting dirty clothes. I don't recognize some of those shirts, and I know no one in the family has ever worn that tie-dyed monstrosity of a dress.
Still, I settle in to the wait as she works. Maybe the unfamiliar clothes are recent purchases Grandmother has made. Hopefully that dress isn't for me, as I don't think I could fake even an ounce of liking for that horrid thing.
When Grandmother gets all the clothes sorted, I expected that the next step would be to load the washer.
But instead of doing that, Grandmother pulled the lint trap from the dryer, and spoke into its slot. "Let the exchange commence."
I shook my head as Grandmother leaned back. Grandfather was right to keep the fact that Grandmother was missing a few squares from her quilt a secret. I should have just left it alone.
But just as I was planning how to never let Grandmother know about my new knowledge, something climbed out of the lint trap's slot.
It looked like a living pile of lint, the dull gray kind that never seems to care what color clothes were in the dryer.
I had to cover my mouth to keep in my gasp.
Either Grandmother wasn't crazy, or a gas leak down here was causing hallucinations.
I wasn't sure which to hope for.
The creature started talking to Grandmother in a language I didn't know, but that Grandmother could apparently speak. As they conversed, other creatures came out of the lint trap slot and started going through the dirty clothes.
But then one saw me.
It let out a rumbling cry that sounded like tennis balls bouncing around in the dryer. At its cry, all the others stiffened and turned toward me.
Grandmother turned as well, and started speaking quickly in the creatures'  language.
The first one replied back with something in its voice that made me shiver.
But Grandmother must have won the argument, for the first creature turned and said something to all the others.
All the creatures stared at me for a moment longer, then retreated inside the lint trap slot.
Grandmother replaced the lint trap, then stood and motioned to me.
I went to her, though I couldn't stop from glancing at the lint trap.
"You'd best head upstairs, dear." Grandmother said sternly. "The dust bunnies don't take well to unexpected guests."