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context: A few days ago, the creator of Gravity Falls and the voice actors went live. One of the highlights was showcasing some of the drawings they created on stream. Among them was a drawing of Stanford and Bill Cipher kissing.
During showcasing that particular drawing, Jason Ritter (the voice of Dipper) literally said, "When you're trying to save... the town." This basically confirms that they have seen the Billford animation. Great heavens o_0