It's good and dead, long live zombie poetry.

Dead as a doornail: Etymology (from wiktionary)

"Probably from William Shakespeare's play Henry VI, Act 4, Sc.10, l.40-1 John Cade: "...and if I do not leave you all as dead as a door-nail, I pray God I may never eat grass more." Although there is some evidence that the phrase was in use before this time.

When doors were built using only wood boards and hand forged nails, the nails were long enough to dead nail the (vertical) wooden panels and (horizontal) stretcher boards securely together, so they would not easily pull apart. This was done by pounding the protruding point of the nail over and down into the wood. A nail that was bent in this fashion (and thus not easily pulled out) was said to be dead. Thus the expression - dead as a doornail"

In other words, the dead doornail is not deceased, only bent. And dodo's, as you observed, are not blue, though embedded links to their skeletons sometimes are