Peachew

I have a 2006 which I purchased last January with 26,000 miles on it. I just hit 38,000 and decided to change the plugs. The trailing ones were unbelievably hard to remove. When they finally came out they had some of the aluminum from the engine stuck in the threads. Also aluminum filings came out with the plugs. Has anyone heard of this before. I was able to install the new plugs and it seems to be running fine.