Tinsel
Tinsel is very attractive to pets, particularly cats. Kitties love this sparkly, light-catching toy. The shiny, dangling decoration reflects light and can move to appear to come alive to watchful critters.
A cat can swallow the tinsel, and this can cause serious injury. Swallowing tinsel can lead to an obstructed digestive tract, severe vomiting, dehydration, and possible surgery.
It is better to brighten the branches with something other than tinsel.