A prototype is the original "proof of concept" for a model. A few can be made, but are even so usually rare. The character cards from 1999 to 2002 generally have pictures of "prototype" models, and also some of the stock photos. There is a controversy as to if the trains that people claim are "prototypes" are actually the demonstrators or just the 1st editions. Some prototypes include the abandoned 6 wheel Toby, the proposed 8 wheel Salty, and the delayed 4 wheel Mavis.
- Most items' prototypes from 2009-2012 seen in order catalogues were from the unrendered computer modelling stage.
- Prototype models can sometimes be seen in pamphlets and yearbooks. This is either a mistake or the final model may not have been produced yet.
- The 1999 tender engine prototypes were images of the 1992 prototypes with plastic coal digitally edited over the painted-on coal on the tenders.
- The 2002 prototypes of many models had visible ledges, despite them being removed that year.
- Most items re-released by Fisher-Price in 2013 used the 2011 and 2012 versions as prototypes.