“ On a planet with an ammonia atmosphere, that is inhabited by intelligent aliens, the police carry oxygen spray, that has the same effect on that planet that pepper spray does here.”
“ There exists a prestigious academy with a history going back hundreds of years. Graduates are highly skilled and very much sought after for employment. For purely traditional reasons, the academy requires its students to become proficient in a skill or area of knowledge that has no use in the modern world. This could be Ancient Egyptian, an antiquated form of writing such as shorthand, knowledge of building or repairing antique steam engines, programming COBOL, etc. PCs who graduated from this academy must be sure to have this skill in their repertoire.”
“ A casual remark by one of the party about something met on a previous adventure leads to a summons to and grilling by the Mages' Guild (or equivalent), probably resulting in an expedition back to that area to recover the things for study by the Guild. The party's presence will be 'requested' for this expedition.”