Originally Posted by the gael
When the asguardian guard returns from the dark elves world, telling Odin That Loki had been killed, look at him, I bet he's Loki in disguise. It Is when he replaced Odin ( they were only two in the room ) Loki has probably created the illusion of being injures by the blade, then he stayer on the ground, so Thor could took him in his arm. After another illusion of his dying body, eh replaced the guard Odin send and then replaced Odin, very simple for him
How is it simple for him to just replace the All-father? Odin isn't exactly powerless, to put it mildly.
Otherwise I agree, Loki took out the guard that went looking for them and assumed his identity.