Pickwickian made me quickly think of picric acid.
http://en.wikipedia.org/wiki/Picric_acid

It's an innocent sounding name. But if you ignore the bottle of picric acid in the back of the store room, salts condense and crystalize in the bottle making it explosive and very sensitive to shock. Not no naive or innocent.

Put some picric acid in your Pickwick tea and you'll have a blasting picknick.

Back in my college days, there was a major emergency in the old Nat Sci building. As someone was going through some old stuff (probably in anticipation of a move to a new bldg), someone came across an ancient jar containing picric. Alarm and consternation ensued. Firetrucks, disposal units, hazmat units, ems personnel, police, etc. Pretty entertaining to those of us safely across the street in the engineering complex. Well, it was entertaining, until we started to wonder what forgotten relics awaited rediscovery in the dungeons of our own castles.

Thanks, Pau, for the Wiki link. I just learned something new.
Sounds to me like:
discovering Picric is no Picnic !!