Way back in the winter of 1977, when Nottingham Forest were doing the same as Leicester City are now and surprising everyone by leading the table, Brian Clough had one regular question for his squad.
It wasn’t quite what everyone else was asking, and whether they could keep it up.
It was the opposite, a clever psychological technique. He wondered aloud wether ‘today is going to be the day’? Would this game be the one in which they blew it, in which the bubble burst.
Today’s game is very different to then, and the threshold has been raised significantly, pretty much to the scale of the quantum leap the sport has taken since then. The opportunities to do what Forest did have been greatly constrained by great quantities of cash at the top end.
Despite that, even in the Premier League era, Leicester are not yet unique.
The following clubs all did similar since 1992-93. They were all the Leicesters of their season - at least until 8 December.
In December 1992, at this exact date, Norwich City were top.
In December 1996, Wimbledon were second.
In December 1998, Aston Villa were top.
In December 1999, Sunderland were fourth.
In December 2000, Leicester City were third.
In December 2003, Fulham were fourth.
In December 2004, Everton were third.
In December 2006, Portsmouth were fourth.
In December 2012, West Brom were fifth but only missing fourth on goal difference.
In December 2014, then, both West Ham United and - perhaps more relevantly - Southampton were occupying fourth and fifth respectively.
All were the subjects of understandably giddy excitement and expectation. All suffered the type of day that Clough talked about. Almost all suffered big falls.
This was where they finished:
1992-93 Norwich: dropped to third
1996-97 Wimbledon: dropped to eighth
1998-99 Villa: dropped to sixth
1999-00 Sunderland: dropped to seventh
2000-01 Leicester: dropped to 13th
2003-04 Fulham: dropped to ninth
2004-05 Everton: dropped to fourth
2006-07 Portsmouth: dropped to ninth
2012-13 West Brom: dropped to eighth
2014-15 West Ham: dropped to 12th
2014-15 Southampton: dropped to seventh
Norwich 1992-93 and Everton 2004-05 are obvious exceptions here since, although they fell down the table, they still enjoyed hugely successful expectation-defying seasons.
For the most part, though, there are common strands to the drop-offs. More moderately resourced sides were able to enjoy a surge over a relatively brief spell when all players were fit and on form and all went to plan, but inevitably struggled to sustain it once they endured a few absences and a few blips.
It isn’t quite so much about “the day” that Clough talked about but an accumulation of those days. Players run out of steam, and find it difficult to maintain a level of performance that was always a bit above their general level, and the perfect chemistry of the team is affected. Once that happens, they don’t have the fail-safes of the bigger sides. They don’t have the same inherent talent or the battle-hardened experience.
There’s also the fact that, after a full round of fixtures, all of the opposition sides have played you and know more about you. The element of surprise goes. Backlines will work out how to defend against Jamie Vardy’s pace on the break.
The one big thing in Leicester’s favour right now, though, is that this remains such a surprising season as a whole.
It says much, after all, that we effectively went six years - from 2006 to 2012 - without a team doing what Leicester or Portsmouth did at this point of the season. That was the spell when money began to talk, when big clubs became super clubs, and cash conditioned the league to a greater extent than ever before.
It came close to guaranteeing that certain sides would reach particular points thresholds, squeezing so many others out.
That looks less likely to happen this season. There are no guarantees.
You can, at the same time, be almost guaranteed that Leicester won’t win the league or even finish in the top four.
At the moment, though, they’re having their day.
Read more from Miguel Delaney