When I was in my mid-20's I was living in a house on farm my cousin leased most of to a cattleman on the next place over. Loud clomping and crashes the old back porch, followed by a loud bellow woke me up one night. I opened the back door and found a cow stuck in the porch, the old floor wasn't able to support her.
I called the farmer and he brought his brother and his boys to get her out, which required a couple of skill saws to cut her a path. They put a new deck on the porch a week or so later, but in the meantime, you could see the series of hoof holes from where she made her midnight ramble up on the porch. I've got pictures of the path she created around here somewhere.
I've seen plenty of goats on roofs, but never a cow.