My Dad used go tie the tree to the wall because our cat would climb up the trunk and then sit and peer out from the branches. When you walked by the tree he would snake his paw out to ambush you. :-)
Our "cow cat" (a sort of "Holstein-looking" b&w shorthair) was the first of our cats to have Christmas tree issues. She would make her way up the tree by threading up through the branches close to the trunk until she found a branch to her liking. Then she would sort of drape herself along the branch and adopt a "waiting for prey" attitude, though she didn't attack anyone. Unfortunately, she was fond of nibbling on ornaments and lights that were within her reach.
She was a good cat who wasn't demonstrative as a rule, but getting her out without destroying the tree or getting bit/clawed in the process was always interesting. She was only with us for six years until renal failure took her, but she made those Christmases memorable. We stopped putting up a tree some years ago, and it is just as well, because the current cat of the house is a male who is very affectionate and attention-loving, but somewhat ornery... I have a suspicion that if we DID have a tree up, his interaction with it would have me warning him that I was about to make him the topper in a direct and most uncomfortable manner.
Mr. niteowl77