Constraining Complexity

The thread of a conversation:
First, my lovely wife and I were lying on the couch after watching an episode of Star Trek: The Next Generation¹, when I commented that her knees were kind of small. She claimed that her knees were normal and in fact that it was my knees which were unusually large and weird. We agreed to disagree. She then started wondering how it was that knee replacements are done². Are all the ligaments and tendons cut and re-attached?  I suggested that perhaps they were moved out of the way and that only the ones attached the joint itself were removed.  She replied that if the joint was titanium, then biological tissue could bond to it and vice versa.  She revealed that she had learned this while reading The Disappearing Spoon: And Other True Tales of Madness, Love, and the History of the World from the Periodic Table of the Elements, which describes the original experiment involving a rabbit and a very thin piece of titanium being placed over its healing leg bone so that the process of how bone marrow produces new blood cells could be observed but not be exposed to the environment.  Creepy.  The scientist³ found that the titanium was bonded to the bone as the bone itself healed.  My wife expressed sadness that a rabbit had been subjected to such a trial.  I agreed, though I suggested that the rabbit had likely been further experimented on to determine the extent of titanium’s ability to bond to bone until the skeletal structure of the rabbit was mostly made up of titanium. Horrifying as this must have been at the time for the rabbit, it now had super powers like Wolverine⁴, and once it had escaped, it could use its powers both for good and to visit a righteous vengeance upon its oppressors and bunny oppressors everywhere. Soon, as its skills developed, all the warning its enemies would receive was a slight rustling in the brush, and then a brief silence as the rabbit launched itself⁵ through the air toward the jugular of its foe.  Later in its evolution, I concluded, the intensive training and its unique bone structure would allow it to achieve sub-orbital flight with a single hop.  The only warning its enemies would then have was the sonic boom the bionic rabbit would create as it re-entered the troposphere⁶.  Unfortunately for them, this forewarning would be unlikely to save their lives.  One hop later, and the only evidence that the bionic bunny would leave behind was the resulting carnage and a few errant hare hairs.
“It needs a name”, my wife said.  “Ellie Junior”, I responded.  “Not very superhero-like”, she responded.  I promised to come up with something more appropriate if something of this sort ever came to pass.
And then I went off to brush my teeth.

¹ Eye of the Beholder, Season 7.  A good one.
² My father recently had one of these, so this wasn’t completely at random.
³ Dr. Per-Ingvar Branemark.
⁴ Snikt, snikt.
⁵ Hop!
⁶ Note: the bunny would require specially-made goggles.