Binyamin Netanyahu shows off his bomb diagram at the UN. Reuters

It was certainly explosive, but did it bomb? Binyamin Netanyahu's show-stopping stunt at the UN general assembly went instantly viral, with memes, remixes and scathing tweets spreading across the internet like shrapnel. But while the ridicule quota was high, there was also admiration.

Twenty-five minutes into his address, the Israeli prime minister reached under the podium and pulled out a folded card. "This is a bomb," he announced – words which in other circumstances might have led to security guards tackling him to the ground.

It was, rather, a crude cartoon of a bomb, complete with fuse, which Netanyahu rather unnecessarily pointed out: "This is a fuse." He then talked through the three stages of uranium enrichment necessary before it could become a real bomb.

Finally in a moment of eye-popping theatricality, he produced a marker pen. After a summer of prodding, pleading, wheedling and commanding the president of the United States to publicly declare a red line for Iran's nuclear programme, Bibi was taking over the drawing board.

"Where should the red line be drawn?" he asked with a rhetorical flourish. Head bent towards his diagram, pen in hand, he went on: "The red line should be drawn right here." And there it was, a thick, shockingly bright red line, across the 90% mark on Iran's nuclear bomb.

"WE HAVE ACTUAL RED LINES," tweeted the journalist Joseph Dana. "Netanyahu is beyond parody at this point."

The Atlantic columnist Jeffery Goldberg had likened Bibi's bomb to Clint Eastwood's chair, referring to the actor's cringeworthy address to an empty chair supposed to represent Barack Obama at the Republican national convention.

A former White House spokesman, Ari Fleischer, tweeted: "Bibi's use of that chart was one of the most effective, gripping, uses of a chart I've ever seen. Is the world listening??"

Most Israeli newspaper commentators concentrated on the consequences of Netanyahu's gimmick.

"Despite all the mocking of various individuals of little faith, the image of the Israeli prime minister and the bomb will be broadcast in every news edition around the world, and will be incorporated in the video clips made by the Republican party for the presidential campaign," wrote Nahum Barnea in Yedioth Ahronoth.

But, he said, "the red line Netanyahu drew is binding for one country. If one takes his statements seriously, within a short time, months at most, if Iran is not deterred and if the US does not attack, Israel will launch an attack on its own."

Ben Caspit, writing in Ma'ariv, said: "The picture of the bomb … portrayed a certain charming childishness, but in the same breath we can determine with certainty that this picture will be broadcast over and over in every language to the television viewers, and Netanyahu, as they say, will have made his point."

The prime minister, wrote Yossi Verter in Haaretz, "did what he does best: he took a complex, amorphous topic and made it simpler, more tangible, more easily absorbed and understood … Was this an effective exercise or was it ridiculous? Helpful or harmful? It's too early to tell. What's certain is that no one can ignore his address, even if they'd want to."

He went on: "The ostensibly comic interlude that we witnessed yesterday … didn't make us laugh. It was black humour. Nuclear humour. And it certainly ought not to distract us from the fact that Netanyahu, for the first time in public, unequivocally set the summer of 2013 as the last chance to stop the Iranian nuke before it's too late."

• This article was amended on 1 October 2012 to correct a misspelling of Ari Fleischer's name.