- Trademarks feature prominently, which means there's a major need to create generic versions (or spoof imitations of) products to avoid clearance costs.
- Many nostalgic characters & objects are still current. The toy comanies know when they've got a hit and they'll milk it for as long as they can. Whether it's Teenage Mutant Ninja Turtles or Transformers, some nostalgic content has been done to death already.
- "I'd forgotten about that!" is a powerful emotion. Taking Koster's Theory of Fun into account, there is undoubtedly a strong chemical process involved in rediscovering atrophied chunk memory. Prehaps the endorphins flow at a greater rate along the already-formed neural links? Whatever the neurophysiological explanation, this feeling is definitely fun.
- Toys & sweets run all the way through. However, for kids from the 1970s, comics & TV are prominent; for 1980s it moves on to films & early 8-bit video games; by the 1990s there is a heavy emphasis on branded characters (cartoons/toys) & 16-bit video games.
As I've noted initial ideas for game spin-offs, I've also realised that there is a pattern to the themes. Some appear to be mostly about aesthetics (e.g. Space:1999 or Fuzzy Felt) and have little actual content that would drive a game mechanic (which doesn't stop them being useful). Others have core factors -- "why we loved them" -- that can be exploited as the core concepts in a game. Many, as mentioned above, need to be converted into an unbranded imitation or gestalt.
Once the useful factors are established, these can be used to drive the game design process.1970s kids' comics are an interesting difficulty here. They are packed with high-concept characters (mostly copyrighed, but that shouldn't be a problem, as parody comic Viz discovered a long time ago) and situations which drive a narrative well. However, they require a very specific art style -- like that of Leo & Martin Baxendale or Tom Paterson -- in order to take advantage of the nostalgic cues. This would undoubtedly require specialist help, possibly from experts in this field like Lew Stringer.
This raises a thought: is it possible to develop a list of steps which can be used to convert any nostalgic theme into a viable game? I suspect that it is possible, and that this is a potential research question.