To the uninitiated, the green frog which appeared on a picture of the Republican presidential standard-bearer and his supporters must have appeared slightly curious.

But on the far-right fringe of US politics there was nothing mysterious about the image of the cold-blooded amphibian - complete with Trump-like blonde thatch - which both Donald Trump Jnr and one of his father's leading advisers, Roger Stone, shared with thousands of their followers on social media last week.

Originally a fun, slacker-like character in a comic book series, Pepe the Frog has more recently been appropriated by the "Alt-Right", a loose, internet-based movement of white supremacists. The once-popular social media meme innocently tweeted by the likes of singer Katy Perry has been appearing in rather less appealing guises. Pepe has been seen with a swastika above his smirk; with "14", the numeric shorthand for "we must secure the existence of our people and a future for white children" over his left eyelid; and, over his right eyelid, "88", which stands for "Heil Hitler".

The Alt-Right - the term was first coined by white supremacist Richard Spencer in 2008 - has, largely thanks to its aggressive Trump-cheerleading, started to emerge from the darkest corners of US politics. Through blogs such as The Right Stuff, its supporters attack so-called "cuckservatives" - a derogatory mashing of the words "conservative" and "cuckold" which they use to describe mainstream conservative politicians who have allegedly sold out white people. While railing against feminism, internationalism and globalisation, the Alt-Right's principal concern is the supposed threat to white identity posed by immigration and multiculturalism, which, they believe, will result in "white genocide".

Trump Jnr's tweeting of Pepe the Frog is not the first time the Republican campaign has been accused of playing footsie with the Alt-Right. In July, Donald Trump caused controversy by Tweeting an image of Hillary Clinton alongside a pile of cash and a six-pointed star, believed to have emerged from an Alt-Right website and carrying clear antisemitic undertones.

The Alt-Right is not uniformly antisemitic. Some ideologues concede the role Jews might play in bolstering white nationalism, while prominent Jewish Alt-Right supporter Joshua Seidel argued in the Forward that Jews are more threatened by political Islam than by proponents of "white civilisation".

Unsurprisingly, however, many of its supporters are deeply hostile to Jews. A popular weekly podcast is named the Daily Shoah, which is credited with creating the triple parentheses meme used to identify Jewish people online.

Alt-Right supporters have trolled Jewish reporters whom they deem critical of Mr Trump with photoshopped death camp images. Jewish "dominance" of the media and financial system is a frequent Alt-Right target, as is conservative support for Israel. As Marilyn Mayo of the Anti-Defamation League's Centre on Extremism suggested to the Times of Israel, while some of the Alt-Right's ideas are not intrinsically antisemitic, "a good deal of the people who are talking about the ideology of white identity, focus on Jews as part of a problem".

While Mr Trump has denied knowledge of the Alt-Right, Stephen Bannon, who was appointed to run his campaign last month, can surely enlighten him. As Mrs Clinton's campaign has pointed out, Mr Bannon once proudly described his Breitbart News website as a "platform for the Alt-Right". By Mr Trump's friends shall you know him.