When David Icke discovered the world was being controlled by a race of reptilian humanoids and/or reptiloid aliens, psychiatrists looked into his past.
Surely some traumatic childhood event must have been responsible for his bizarre ramblings about the Babylonian Brotherhood, they reasoned.
They didn't have to look back very far. The legendary conspiracy theorist was once a talented goalkeeper. That says it all.
He played between the posts for Coventry City and Hereford United before going on to discover that aliens were living among us.
All part of a natural career progression if you ask me.
As any good psychiatrist knows, goalies aren't just a different breed - they're off-the-scale crazy.
Which brings me to the ongoing feud between two other candidates for a permanent vacation at Alberta Hospital: Oliver Kahn and Jens Lehmann.
The duo, competing for the job of Germany's starting goalkeeper, have been throwing their toys out of the pram because their national coach hasn't decided which one of them is more mentally unstable (and thus better suited to the job).
Former players say the pressure is forcing Kahn to make mistakes. Despite the fact he's played in World Cups and European Championships, apparently the stress is too much for him to bear.
But Kahn himself had a different explanation for his latest clanger, which cost his club team Bayern Munich a 1-0 defeat against Juventus last week: a wet ball, wet grass, a bad bounce and the fact that an alien obscured his view (OK, I made the last bit up).
Lehmann, for his part, seems to be in the midst of a mental crisis that gets worse with each successive howler. And his club team, Arsenal, is starting to pay the price.
"The Germans gave the world Beethoven, Claudia Schiffer and Michael Schumacher," wrote the English Sun. "Arsenal, sadly, got Jens Lehmann."
Lehmann's erratic form - and temper - hasn't stopped him from trying to prove his eligibility for the top job by lashing out at Kahn.
He recently referred to 34-year-old Kahn leaving his wife for a woman he met in a disco by saying "I don't know what we have to say to each other.
"I don't have a 24-year-old girlfriend. I live a different lifestyle."
This must, by his own logic, mean he is a better ... er, player. Right?
"I can't really say that anybody else is better than I am," said Lehmann, modest as ever.
Kahn responded by saying that Lehmann just "can't cope with being the number two, he doesn't seem to be able to live with it."
Other players are used to competing for the same position. But not goalkeepers.
Different breed, you see.
Mentally unstable. And prone to having alien encounters.
Goalies are also prone to some of the most bizarre injuries in the history of soccer.
In 1975, Manchester United keeper Alex Stepney was shouting so hard at other players that he managed to dislocate his jaw.
BOTTLE OF AFTERSHAVE
Spain's Santiago Canizares injured himself by dropping a bottle of aftershave on his foot. And former Wimbledon keeper Dave Beasant suffered the same fate after failing to hold on to a salad cream bottle while making a sandwich.
But if Kahn or Lehmann are looking for a less physically painful excuse for a holiday, maybe they should consider the example set by England keeper David "Calamity" James.
James said he "injured" his concentration while playing too many video games.