What's got two legs and really annoys Jurgen Klopp?
No, it's not referee Paul Tierney, although fair play if that was your response.
Instead, the correct answer is a gripe that has been long-standing with the Liverpool boss, so to speak.
The League Cup semi-finals.
“I think it will be better with one game absolutely, but obviously what is say is not important,” said Klopp last month, mere minutes after his side had set up a last-four showdown against Arsenal by beating Leicester City on penalties.
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“Look, I have been speaking out about player welfare not just this year, but for the past six years or longer. But the only thing I do is to create headlines not change.
”Of course I would prefer one game and the draw is at Arsenal first so fine, we can play there and see who is better and go from there. But I really can’t see any changes to be honest.”
Klopp is, of course, speaking from experience. This is the third time in seven seasons he has led Liverpool to the last four, beating Stoke City in 2016 but eliminated by Southampton the following year.
And the postponement of the first leg at Arsenal - due to be played tonight but called off because of the COVID outbreak affecting Liverpool - has brought the fixture again into sharp focus.
Last season's congested calendar meant the semi-final became a one-off match. Nobody complained, although with no supporters in the stadium the venue mattered little.
But this campaign's reversal to two legs - as it has been for every other season in the competition's history - prompted inevitable sighs of discontent in certain quarters, particularly given fears of how the pandemic could again affect the schedule.
So it has proved, although gaps in the calendar - made available by the scrapping of FA Cup replays - mean the semi-final should be completed as intended.
The early rounds of the League Cup used to be played over two legs until they were phased out, as too were replays including the final - Liverpool were involved in such games in 1978, 1981 and 1984.
Perhaps the time has come, then, for the semi-finals to become a one-off game - not least because the EFL are missing a trick.
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FA Cup semi-final weekend used to be one of the highlights of the year, matches played at neutral venues between teams hoping for a chance to appear at Wembley. Supporters loved it, and it made for some fantastic television viewing.
Now, as it has done for the past few decades when available, the national stadium hosts both matches, at a stroke diminishing the magic of the round and the achievement of gaining a final spot at Wembley.
The League Cup, then, could follow the old FA Cup example and have semi-finals as a one-off game at a neutral Premier League stadium.
It's not as if there aren't enough potential venues in the modern era. And what would, by today's standards, be an unusual sight of two teams thrashing it out at a neutral ground in front of a crowd split 50/50 under the floodlights in January is enough to warm the hearts of any football fan, let alone Klopp.
You know what to do, EFL.
