[3] However, Ben Black Elk was known to be merely earning his bread as an actor by having taken pictures of him with tourists near Mount Rushmore for money,[4][5] also starring in the 1962 film How the West Was Won.

[6] Upon Vogel's departure, Ben Black Elk allegedly gave him a farewell present: a handful of seeds of Echinacea purpurea (purple coneflower).

[9] Jan Willem Nienhuys claimed that he obtained his honorary degree from California University of Liberal Physicians (CULP) situated in Los Angeles, an institute that was dissolved long ago and whose legitimacy of its diplomas is disputed.

[10] On October 14, 1982, Dutch teacher, presenter and comedian Ivo de Wijs [nl] published an article in the science section of NRC Handelsblad on this matter, in which he branded Vogel a quack.

[10] Vogel was criticized for justifying his opposition to blood transfusions by claiming that they could lead to a change in character in older editions of Der kleine Doktor (published in English as "The Nature Doctor").