Government-enforced electricity outages or ‘loadshedding’  have been in place since 2008 to manage Pakistan's electricity shortage. So when the lights first went out, many responded by powering up their generators or lighting candles, thinking it was a scheduled outage. Until tweet after tweet came in reporting that practically the whole country had been affected.
The news was verified almost instantly by journalists like Faizan Lakhani (@faizanlakhani ) on Twitter:
@faizanlakhani : Confirmed: #Karachi  #Lahore  #Islamabad  #Rawalpindi  #Mangla  #Dina  #Faisalabad 
#Sialkot  #Quetta  #Hyderabad  #Peshawar  are suffering #blackout 
On the night of the outage, six power plants were working around the clock to meet the demands of the 180 million strong country. And when one plant got stressed out and shutdown, it set off a domino effect across Pakistan's national power grid .
Load sheddings (rolling blackouts) are quite common in Pakistan and are wildly unpopular. Reports  suggest government mismanagement:
The government does not want to upset voters so there are no planned outages to manage the electricity shortage …[Sunday] was bound to happen. You can’t keep people happy with an uninterrupted power supply when surrounded by so many problems.
One of the first people to suggest that this power failure was on a national level was Samra Muslim (@samramuslim ) with this tweet:
Soon social media in Pakistan was buzzing with queries to the online Twitter account of the Karachi Electric Supply Corporation @kesc_ltd .
When most of Pakistan aside from the high-security red zone and military bases remained shrouded in darkness, people once again turned to humor to make life easier during the blackout. As hilarity ensued, even our neighbors joined in on the puns:
With umpteen promises to turn the power back on within hours and people ranting and raving about all kinds of conspiracy theories from an army coup to an alien invasion, day light finally brought with it the sanity of restoration to the national grid. As city after city came back to power, Pakistanis realized that even the darkest night in our history could be seen through with unity to laugh in the face of helplessness.