John “Three Continents” Watson
This fan-created nickname has its origins in the Sir Arthur Conan Doyle novel The Sign of Four, in which Doctor Watson boasts “an experience of women which extends over many nations and three separate continents.”
Further details of the good doctor’s lady-killing history are never discussed, making it unclear whether he is simply an unapologetic whore or whether he has had many brief and ill-fated past marriages. Regardless, one can be reasonably assured (given the rather characteristic Victorian stiffness of vocabulary) that Doctor Watson had more than made the acquaintance of aforementioned women.
In fandom, this moniker is most often referred to in fanfiction (a notable culprit being Atlin Merrick) and is used as a testament to John Watson’s sexual experience, which generally goes hand-in hand with sexual prowess.