I wasn't gonna say anything, but I had the Grimace shake before I saw all of you whining about it, and it wasn't bad. I was like, "what is wrong with you sissies?" Then I got another one and I noticed something...The first one I had was a light purple, swirled with a little bit of the white of the ice cream. The second one was a dark radioactive solid purple, and it treated my body very differently than the first.
Either some places are putting in too little Grimace batter, or some places are putting in too much Grimace batter. I don't know which one was 'correct'. Most of the official promo images seem to show the 'lighter' version, though.