The biggest day of the competition. Grander fun that the final itself, when only two clubs get to feel like it's their birthday.
The fourth round is the Scottish Cup's Christmas Day - everybody gets a present.
The big guns come into the competition to join the Cinderella outfits that have been battling through since the days were long and the evenings were blessedly gentle.
For some, the road to Hampden is long and weary.
It's a wonderful day.
Only one club survives from round one back in September: the itinerant Auchinleck, who won that afternoon at Lossiemouth.
Now the Talbot are visiting Tynecastle - the kind of fixture that has fairytale written all over it, although Hearts would do well not to apply the noun "fairy" to anyone from the Ayrshire village.
And brilliant though it is, the mind races at the prospect of that tie having been drawn in reverse order, or for that matter, a replay.
This would lead to all sorts - not least the sudden birth of Heart of Midlothian supporters clubs - in neighbouring Cumnock.
In fact, I have often considered what a wheeze it would be in the competition if, when clubs from different divisions are drawn together, the tie is automatically played at the home of the lesser club.
For example: Peterhead hosting Celtic and Rangers at Arbroath fascinate. The fisher folk travelling to Glasgow would, frankly, be yawn-inducing.
It is the fact that Hibernian, stuttering and stammering in the Scottish Premier League, have to go to Cowdenbeath that adds the spice.
They may yet emerge from Central Park as battered and bruised as the stock cars that race there.
That is the tie which most looks most likely to persuade the Sunday morning newspaper men to inflate their headlines.
Except of course there is a logic that says, if you expect something then it cannot be considered a shock at all.
So where else would you cast your eye in search of the scoreline that makes you gulp?
Aberdeen at Forfar's Station Park?
Surely the Dons are once again on the straight and narrow?
Ayr United are at Livingston and that too would have been better in reverse given that Somerset Park has been the graveyard of SPL clubs in the League Cup.
But Dundee hosting Kilmarnock could be tasty.
Wherever you go, wherever you lay your affections, don't you just love this date in the calendar?
It was the fevered day that spawned BBC Radio Scotland's ever more popular "Open all Mics" programme, the effervescent version of Sportsound that does what it says on the tin.
At the fourth round of the Scottish Cup - and, indeed, beyond all the way to the quarters - we sent reporters to each tie and left the faders open all over the country, which led to a delightful mayhem as goals were shouted in from Wick to Wigtown.
It was such a smash hit that we adopted the recipe for the Scottish Premier League on a weekly basis.
Meanwhile, given that I have tipped Celtic for the domestic treble, I can hardly bodyswerve Neil Lennon's side as my tip to lift the old trophy, although my annual and long-held preference is that neither they nor Rangers embrace it on final day.
It is just that, for me, it is a special thing when the winners come from a place that allows a victory parade. Just call me old fashioned.
But let's not spoil the party. Open All Mics returns to its roots this weekend and I am so up for the Cup.