More often than not, the BK shake machine broke down, especially when I worked there.
Way back when Ray Kroc sold shake mixers to the McDonald brothers (thus creating fast food history), shakes were made with milk and ice cream.
At BK, the shakes were made from this prefab powder. God only knows how many chemicals were in it.
Friendly’s still makes good shakes. There’s also an ice cream stand by me called Cliff’s. They’re one of the few places you can actually get malts. Thick enough to bust a straw.