I was listening to the Blizzcast, and at the very end they talk about the Secret Cow level.
From about 10:22 he talks about a skeleton of the Cow king, and then he teases and say; maybe we will have to cut it for a lack of interest. Implying that the cow level is actually in. The interviewer then mentions having to find it ourselves.
Secret Cow level is in I dare say.
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