Oh no! Well, this could be a couple of things. Firstly - if the pan hasn't been well greased or floured (or sprayed with a trusted non-stick spray), I'm afraid sticking is inevitable. If the pan has been well-prepped, sticking can still occur, especially if you've not let the yellow squash muffins cool a bit before trying to remove from the pan. Hot muffins fresh from the oven are difficult to handle and prone to sticking due to the moisture. You may also find that the muffins stick if the pineapple hasn't been well-drained - again adding too much moisture to the batter. This in turn can make them more difficult to bake through and more troublesome to get out of the pan at the end!