Thing 1 became attached to a stuffed Eeyore beanie baby when she was little. She slept with it until it became sad looking and abused, very Velveteen Rabbit real. She has since adopted other special stuffed animals. Not every one that passes through her hands makes the cut, but enough do that she has a sizable pile that sit on the top bunk who are possible sleeping companions.
In order to not offend anyone, Thing 1 started keeping track in a little log she drew up and kept by her bed. She listed the name of each stuffed animal and gave it a tick mark on the grid each night she slept with it. She faithfully noted and rotated and the stuffed animals for a couple of years.
I haven't seen the log lately, and she seems to be choosing her sleeping companions based on the mood of the evening.
Thing 2 goes in phases. She picks an animal and sleeps almost exclusively with it and only it for a couple of months. For a long time now it has been Princess, a stuffed horse my sister gave her when she turned two. Horses have always held a special place in her heart, and I think she feels the largeness of the stuffed horse provides a sort of barrier between her and any intruders who might pose a threat to her at night.