There used to be a place in the town where I grew up that advertised "burritos as big as your head," but they did not take large-headed people like myself into account. The burrito was smaller than my head.
There is a place here in Seattle that has pictures of their burrito grande next to babies and they are of equal size. Somewhat ironically the restaurant is name Gordito's Healthy Mexican restaurant.
There used to be one in Kalamazoo MI on the west side of the WMU campus in the 90's. Loved that place, burritos were really good. No, not really as big as your head, but it was a lot of food.