During one of his installments of Iwata Asks, the late president of Nintendo, Satoru Iwata, interviewed Tsunekazu Ishihara and Shigeki Morimoto concerning the premier of Pokémon HeartGold and SoulSilver. Ishihara, the president of The Pokémon Company along with colleague, Shigeki Morimoto of Game Freak sat with Mr. Iwata where the pair spilled the "bits" about Mew's origin.
I vaguely remember reading this article in the past. I'm glad I stumbled upon it. However, the segment where they mention Mew reminds me of the exploitation of Pokémon VG and why most of us have come to join the PPorg community. I'll leave the link below if you all would like to read the transcript.
http://iwataasks.nintendo.com/interviews/#/ds/pokemon/0/0