Dogecoin is currently 29th in Market cap. Its's price on 21st of december is $0.007472. Market cap $840,027,091 USD. So how the coin that was originally intended as a joke became so popular?

introduction

Dogecoin was first introduced on 6th December, 2013. Billy Marcus wanted to create a 'fun currency', mainly for the reasons to differentiate DOGE from other cryptos, and Bitcoin especially, as for the december 2013 it was seen as a 'drug money' due to its close ties with Silk Road.
They got together with Jackson Palmer and created dogecoin.com with DOGE logo and Comic Sans text beneath.
That's how their site looked like back in december 2013

So, initially dogecoin was a fun and entertaining cryptocurrency

how it worked, differences with bitcoin

public blockchain ledger, just like Bitcoin. You can check transactions here
its mining structure is based on scrypt algorithm, just like Litecoin.
there is a tenfold difference with bitcoin with the block generation time. In DOGE the block is generated every minute

amount of DOGE

from the beginning it was planned to generate 100 billion DOGE, but then the plans has changed. Now it is inflational currency, which means that there is no end to coin production.
rate of inflation in 2015 was near 5% per year, since then it decays every year.
Nevertheless we can see the price going to the moon since Septemper 2017.

usage as a tip on Reddit and crash of 'dogetipbot'

DOGE coins were used to 'upvote' posts in Reddit(just like in steemit). It was one of the most popular tipping system on the Internet with 52,000 people using it. John Muhlmed suggested to create a company based on that. He didnt get investor's support, and when he ran out of money he suggested to use user's monies.
Company Wow such business inc. got bankrupt. With that huge volume of DOGE coins.

After that DOGE was freefalling for a couple of months. But now the price rose to before-dogetipbot standard

Resteem and upvote if you liked it, I appreciate your attention.