Pony and nerd news with everything in between.
YouTube did the same thing to me once. I actually have two separate channels both named "GoldenSandslash15" because of it now.And I hate that, cause it means that I can never tell which one I'm using.
It's baffling why this is even a problem. This should be something you can opt into, (having multiple accounts under the same email) not be forced into.