The reckless abandon of the investing world has a new fixation: a cryptocurrency that initiated in 2013 as a joke, was mostly forgotten, and thanks to a swirl of tweets from Tesla Inc. Chief Executive Elon Musk, is suddenly worth a total of more than $6 billion.It is called dogecoin, a homage to bitcoin that was designed to serve no real purpose. Dogecoin holders can’t buy much with it and can’t simply convert it to cash. For most of its life, the virtual currency has traded for no reason other than to generate online laughs. Dogecoin is named after an internet meme that appeared almost a decade ago. The meme centered around an image of Shiba Inu dog with poor spelling habits (thus doge instead of dog). Users Photoshop the dog’s furry face onto everything from astronauts to Twinkles.In 2013, the software developer Billy Markus was watching bitcoin gain in popularity and decided to make his own lighthearted cryptocurrency. He first based it on the videogame “Animal Crossing,” and named it bells, named after the game’s pretend currency.