My favourite morphing memory must belong to Bonnie Ray Williams.
In the immediate aftermath of the assassination Bonnie Ray completely forgets that after the men working on the sixth floor broke for lunch, he went back up to the sixth floor alone where he spent about 25 minutes having his lunch while waiting for the motorcade. Instead, his memory morphs into going down to the first floor, collecting his lunch and going back up to the FIFTH floor with Hank Norman and Junior Jarman. His time spent on the sixth floor alone, eating his lunch, seems to have vanished.
The very next day he is interviewed by the FBI and his memory once again morphs - this time he remembers going up to the sixth floor alone but not having his lunch. Instead, he had a quick look around, saw no-one was there and went down to the fifth floor. He was only on the sixth floor for about 3 minutes.
On January the 8th he is interviewed by the FBI again and his memory morphs again - he now remembers having lunch on the sixth floor, he is up there for about five minutes before going down to the fifth floor where he spends about 25 minutes with Hank and Junior waiting for the motorcade.
By the time of his 3/19/64 FBI interview his time spent on the sixth floor appears to have completely slipped his mind.
As impressive as his speed-morphing memory is up to this point, it's nothing compared to his WC testimony. When asked how long he was up on the sixth floor, Bonnie Ray replies "5, 10, maybe 12 minutes". Later in his testimony Bonnie Ray is asked what time he went down to the fifth floor, to which he replies "10 or 15 minutes after 12". He then breaks his speed-morphing memory record, after a single question:
Mr Ball: Approximately what time was it?
Mr Williams: Approximately 12:20, maybe.
From not remembering being on the sixth floor at all, to remembering he went up there but didn't have lunch, to remembering he went up there and did have lunch, to remembering he was up there for 3, 5, 10, 12 then 20 minutes, Bonnie Ray demonstrates a truly impressive ability to morph his memory.