Conkers are definitely the chestnuts, they are ubiquitous in England, where Adams spent a lot of time, and a well understood reference to a childhood game here.

Conkers are definitely the chestnuts, they are ubiquitous in England, where Adams spent a lot of time, and a well understood reference to a childhood game here. A film that recently did the unlikely events driving the plot device very well was Everything everywhere all the time. It never occurred to me that they could have been inspired by Douglas Adams.