Our Saint Bernard when I was a kid would always lie in the doorway between the kitchen and the rest of the house. At 185 pounds, she was a lot of dog to step over, but step over we did! But when my grandfather was visiting, as soon as he stood up, she awake from a seemingly sound sleep, move out of the doorway until he passed through, then go right back to sleep back in the doorway again. He had bad arthritis in his joints, and walked with a cane - he couldn't have lifted his foot high enough to get over her anyway ...
so she'd move for him, but no one else! And trying to move her by pushing was like pushing on 185 pounds of jello - she'd just go limp, so push on one part, fine, but the rest of the dog didn't move!