Twitter has suspended more than 1,500 spoof accounts featuring grey, expressionless avatars known as “NPCs”.

Each one takes a character known as “NPC Wojak” for their profile picture - carefully modifying his appearance to incorporate a rainbow Mohawk, hipster beard or tortoiseshell glasses - and tweets bland, politically correct pronouncements such as “Diversity is our strength!”

But what is it all about? What is an “NPC” and why was Twitter so quick to shut down such apparently harmless fun?

“NPC” stands for “Non-playable character”, a phrase taken from video games referring to any figure a gamer encounters while roaming a digital landscape that they cannot control themselves.

Rather than the hero of the game, these are often supporting characters who offer a quest or recite dialogue to further the plot. Unthinking automatons, they have no minds of their own.

The slang - “born in the fever swamps of 4chan and Reddit message boards”, as Kevin Roose of The New York Times puts it - has been adopted by right-wing social media users, many backers of President Donald Trump, as a means of attacking conformist liberal voters ahead of the 2018 midterm elections.

I love @iamjohnoliver! He’s so funny and is so smart! Keep it up @LastWeekTonight! pic.twitter.com/yY7LlcJ9Zd

— NPC8842674672 (@npc8842674672) October 16, 2018

Like “snowflakes”, “cucks” or “libtards”, “NPC” has become a popular insult for criticising Democrats and other left-leaning web users, accusing them of being unable to think for themselves, parroting orthodoxies of inclusivity rather than challenging mainstream assumptions.

When liberals take exception and accuse the trolls of dehumanising them, their taunters simply hit back by saying they have no sense of humour, therein proving the validity of their initial witty barb.

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WE ARE ALL REAL PEOPLE WITH REAL THOUGHTS!! pic.twitter.com/p1H80KuhLI

— NPC#11146783 (@N11146783) October 16, 2018

The criticism may be crude, but it could also be argued well-worn insults about President Trump being “orange” or laughing at his family changing their surname from “Drumpf” — as encouraged by satirist John Oliver — are similarly lacking in originality.

For its part, Twitter has quickly cracked down with the midterms just weeks away over concerns about the spread of misinformation.

Interference from Russian bots and fake news factories channelled through social media caused a scandal after the 2016 presidential election and Twitter is anxious to avoid repeat accusations about its role in disseminating misleading information and propaganda.