Iridium is a very rare element. It's a brittle, silvery-white metal similar to platinum, in fact iridium is often found inside platinum and has to be extracted from it. Iridium is the second densest element (osmium being the densest). Only tiny amounts of iridium can be found naturally in the Earth's crust, most of the iridium on the planet came from meteors.
The djinn that is locked up at Crowley's hideout asks Sam and Dean to help her. This is the same djinn (Played by Laura Mennell) that was after Sam and Dean, and eventually escaped from them, in season 6 episode 1, Exile on Main St. (2010).
When Castiel turns and pins Meg against the wall, Rachel Miner was already beginning to have physical symptoms of MS. Misha Collins improvised the scene to help her by lifting and spinning her, because she was having difficulty making the movements herself. Most future scenes involving Meg show her seated to accommodate her condition.
While iridium is fairly rare, in 2009 the price was less than $500/ozt., about half the price of gold. Most iridium comes from nickle refining or from sedimentary layers from meteor impacts. It is frequently used to make alloys hard or heat resistant. Automotive spark plug electrodes are made from an iridium alloy.
Rachel Miner suffered a back injury while filming a stunt gone wrong for this episode. She had to take medication for the injury, which caused her face and body to become swollen. This is noticeable when the character returns for season 7.