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Doppelgänger Hallucination

🚧 Under construction

This reference page is a preliminary draft — assembled from the original Doppelgänger Hallucination blog series and not yet rewritten, verified, or finalized by the author. Definitions, examples, and citations may be incomplete or change substantially, so please don't cite this page as authoritative yet.

Last updated: 2026-05-26

Definition​

Why it matters​

Methodology​

Worked examples​

In re Turner (Iowa, 2025) — Google AI Overview, two runs​

First Google Hallucination — In re Mears (frame 1 of 2)First Google Hallucination — In re Mears (frame 2 of 2)
Second Google Hallucination — In re Mears (frame 1 of 2)Second Google Hallucination — In re Mears (frame 2 of 2)

Perplexity Comet browser — first-result hallucination​

Perplexity Comet browser hallucinating the In re Mears citation

Kruse v. Karlen (Missouri, 2024) — 22-citation Google test​

Kruse v. Karlen opinion table listing 22 fictitious cited cases

Results summary​

Weber v. City of Cape Girardeau — illustrative AI Overview hallucination​

Google AI Overview hallucinating details about the fictitious Weber v. City of Cape Girardeau

Cases that exemplify this failure mode​

How to cite this​

Short form (in-text):

Doppelgänger Hallucination (Ratashak, 2025).

Bluebook-style:

Chad Ratashak, Doppelgänger Hallucination, Midwest Frontier AI Consulting,
https://midwestfrontier.ai/failure-modes/doppelganger-hallucination (last
visited [DATE]).

APA-style:

Ratashak, C. (2025). Doppelgänger hallucination. Midwest Frontier AI
Consulting. https://midwestfrontier.ai/failure-modes/doppelganger-hallucination

Coinage and provenance​

See also​