[[WMG: Hercule Poirot is the ancestor of [[Series/{{Monk}} Adrian Monk]]]]
Two Words: SuperOCD. Perhaps Poirot and Countess Vera Rossakoff had more than a little admiration for each other...

We know from canon that Sherlock Holmes had French relatives; could he, perhaps, have had BELGIAN relatives? Perhaps that is why Poirot didn't go back to Belgium after the war, if he had relatives, albeit distant ones, in Britain.

[[WMG: The detective we see on screen is not Poirot]]
Whoever he is, he refers to Poirot in the third person. Is it possible that Poirot is really like Mycroft Holmes, a figure hidden from the world and only in contact via an accomplice?

[[WMG: Poirot wears [[spoiler:a fake mustache in ''Curtain'' because he lost the original in ''The Big Four'']] ]]
After [[spoiler:faking his death due to a explosion Poirot disguised himself as Achille in that disguise he had a scar in a location where it would impossible to grow a mustache as such he'd obviously have to wear a fake mustache for the rest of his life just like he did during the first part of his Achille act, that's why he had a fake mustache in ''Curtain''.]]

[[WMG: Achille Poirot actually exists]]
In one of the short stories, Dr. Burton remarks on the odd naming convention that Madame Poirot gave to her son''s'', indicating that Poirot does have a brother, and Poirot is likely just "borrowing" Achille's identity while being undercover in ''Literature/TheBigFour"

[[WMG: Poirot was [[spoiler:Norton's final pawn in his stream of murders by proxy.]]]]
When Poirot presented his belief that [[spoiler:Norton was murdering by proxy Norton]] smirked and seemed unconcerned by [[spoiler:Poirot]]'s plan to [[spoiler:execute]] him. [[spoiler:Norto was planning on corrupting the Great Hercule Poirot into a Murderer]] from the beginning!

[[WMG: The Darwin Awards have an entry for [[spoiler:Mlle. Blanche]]]]
That series of murders was all over the headlines, and blackmailing a murderer? [[TooDumbToLive Seriously]]?

[[WMG: Hercule Poirot is a Time Lord]]
It would explain his curiously extended career and very high intelligence (and perhaps some of his quirks). Furthermore, by this WMG, Hastings, Japp, and Miss Lemon are his companions. After [[spoiler: ''Curtain'']], he left earth to carry his trade to the wider space-time continuum.