Fan speculation about the other Elements, particularly ones that were mentioned only in passing and/or during the title sequence, could fill several chemistry textbooks.
Harsher in Hindsight: The present-day ubiquity of cameras, especially in London, makes Steel's admonition to never have another photo taken a lot more difficult for Liz to comply with.
Nightmare Retardant: Assignment 3 has a cliffhanger where Steel is attacked by... a pillow.
Paranoia Fuel: Any sufficiently large assemblage of old objects can potentially summon an Eldritch Abomination to destabilise the universe. Beware of museums... (An alternative interpretation of Assignments One, Three, and Five is that it's old-fashioned lifestyles or attempts to re-enact the past that cause problems, rather than simply collections, although this is not true of Assignment Four.)
Star Trek Movie Curse: Assignments Two, Four, and Six are generally regarded as being better than Assignments One, Three, and Five.
