The Daltons' Amnesia (Volume 49) (Lucky Luke, 49);

The Daltons have forgotten who they are—even Averell isn’t hungry anymore!

After a fellow inmate, having received a blow to the head, forgets his own name and is freed as a brand new man, the Daltons start pretending to be amnesiac in order to escape the prison. So as to test their supposed amnesia—and hopefully allow them to retrieve their memories should it be real—they are put in familiar situations: bank hold-ups, train robberies … under Lucky Luke’s supervision, of course.