Cross-prompting, “anomaly placeholding”, or just “prompting” is a compositional technique wherein a future series slot is used in a work of containment fiction, prompting its eventual creation based on the context of the initial use. For example, if in a theoretical RPC-2830 article, a not-yet created “RPC-3042” is mentioned as being a sentient weather phenomenon, a future RPC-3042 would be written based on this prompt.

The collaborative nature of many containment fiction projects lends itself well to this compositional method, and is a challenge for future writers in that gives a prompt that they must work with when writing. Cross-prompting technically includes the use and context of the prompt when populating the new article; simply using a previously-referenced slot number at a later time with no relation to its initial mention is not cross-prompting. Cross-prompting is also distinct from retroactively including a cross-test or cross-link to an already-established article.

Cross-prompting has been around since 2008, when on 4chan’s /x/ board, other SCPs were encouraged to be included in articles, and then written ex-post-facto with the cross-testing/referencing in mind.^[1]https://archive.ph/jmVa6#selection-6151.176-6151.287 The first containment fiction work to utilize cross-prompting was the initial (non-viable) SCP-314. It mentioned a “SCP-497”, which was then written based on the prompts in this SCP-314.^[2]https://archive.ph/jmVa6#selection-9983.30-9983.44

Archived commentary on EditThis shows that cross-prompting was expected of authors:^[3]http://web.archive.org/web/20080715203430/http://editthis.info/scp_wiki/Talk:SCP-016

“If you reference SCP-222, you had better damn well WRITE SCP-222!”

Other examples of cross-prompting include SCP-002/SCP-003, and SCP-3309/SCP-4463/SCP-4463-J.