Well that may have been one of the trickiest April Fools jokes I've ever seen. Starting the challenge on April Fools' Day, and then offering a little gift? What a limbo idea...
I hate you google. I had all 150 pokemon and when I went to a place where Mew was he would not show up on my phone. I wish they would be nice and give to the people how got all 150 and not 151. I would of got it but due to a glitch or something Mew didn't show for me.