It looks like Niantic may have patterned the Pokemon that players can get on "Pokemon GO" when they hatched the 2 Km egg from an old Pokemon Game. The Pokemon found in the first part of "Pokemon Red and Blue" game is also found in the 2 Km egg.
According to Otakukart, "Pokemon Red and Blue" begins with a choice of either Charmander, Bulbasaur or Squirtle from Professor Oak. All three Pokemon can also be acquired in "Pokemon GO," by hatching the 2 Km egg.
The connection only begins there as the players move along in "Pokemon Red and Blue," they will encounter wild Pokemon such as Pidgey and Rattatas. Moving further, they eventually encounter Caterpie and Weedle as well.
Once the players reach Viridian's forest, Metapod, Pikachu and Kakuna are now encountered. The will be followed by Spearow and Jigglypuff in Route 3. And finally Geodude, Zubat and Clefairy will all be encountered in Mt. Moon of the original "Pokemon Red and Blue."
The only Pokemon encountered in the original that's not in "Pokemon GO's" Pokemon lineup to be hatched from the 2 Km egg is Paras. But he is replaced by Magikarp, which has a good reason why he's available in the 2 Km egg. It takes a lot of candies for him to be evolved.
Is this all a coincidence on Niantic's part? Probably not, as the evidence is too compelling, save for the Paras exclusion and the Magikarp inclusion in the 2 Km egg.
Why would Niantic do this? No one really knows, maybe the developers of "Pokemon GO" are really a big fan of the original "Pokemon Red and Blue," which would put some sense into this connection.
But at least players now have an idea on Niantic's reasons for putting those Pokemon to be hatched in the 2 Km egg of "Pokemon GO," it's because of the original "Pokemon Red and Blue." Speaking of "Pokemon GO," Gen 2 Pokemon has arrived and here's everything you need to know.