Expando-o-Ducks are metal ducks created by Blitzen that, when a button is pressed, grow significantly.
Magnus Chase and the Gods of Asgard[]
The Sword of Summer[]
When in a crafting contest with Junior, Blitzen at first makes Expand-o-Ducks as a result of stress as it was well-known that Junior was the best craftsman of the Dwarves.
The Ship of the Dead[]
When fighting Jotunn and Wights on Naglfar, Blitz uses his Expand-o-Ducks to fight the army. When the giants allow a ceasefire for the Flyting between Magnus Chase and Loki, the captain of Naglfar, Hrym makes sure the Expand-o-Ducks are not used, as they cause great fear in the ranks of the dead and undead.