Honduras, December 1920 was an unproduced episode of The Young Indiana Jones Chronicles, which would have been part of the third season of the series. The subject of this episode was to have been archaeology. The historical figures Indy would have encountered are Herbert Spinden and Frederick Mitchell-Hedges.
In this episode, while on a field trip with Herbert Spinden, Indy would for the first time (chronologically) encounter the rival archaeologist René Emile Belloq and depict their discovery of a crystal skull in the ruins of a Mayan city. Their relationship was to start out friendly, but Belloq steals the skull and sells it to adventurer Mitchell-Hedges.
It's possible that this episode would have explained the events that, according to Indiana Jones and the Temple of Doom, caused Indy to be accused of being a grave robber instead of an archaeologist, while on an adventure in Honduras. This has since been attributed to events surrounding the Crystal Skull of Cozan in the opening chapter of the Indiana Jones and the Philosopher's Stone novel.
The crystal skulls have been incorporated into multiple Indiana Jones stories over the years since, and Lucas himself finally dealt with the skulls in 2008's Indiana Jones and the Kingdom of the Crystal Skull which included the archaeologist explicitly pointing out that the Crystal Skull of Akator was not the Mitchell-Hedges Skull.