There was no forking of the Doge main net. A hark fork means there would be two distinct chains coming off from the main net chain, and normally one takes over the other by consensus of the network (for example the chain with the more miners/hashrate). 

This is not the case with Dogethereum. This is a completely separate coin/chain that has no connection (you can't follow a block explorer back to the original chain) with the doge network whatsoever. It just gave some users free coin by "insta-mining" the equivalent number of dogethereum on its own network to match at a 10000:1 ratio with what a user had in their wallet on the doge mainnet at/or before block 2157611. It simply did this by looking up your doge wallet balance on doge's main net explorer with the private key that you provided. 

Please don't confuse this with being a fork at all. Otherwise the exchanges that all running doge right now would have to have updated their daemons.