Although in the credits are listed two directors, 'Kulový blesk' was in fact standalone debut of Ladislav Smoljak. According to Smoljak, Zdenek Podskalský only backed his project with his name as so-called directing supervisor because Barrandov Studios was afraid to entrust the feature film into hands of inexperienced director.
In one scene Zdenek Sverák as Dr. Jecny dictates to other people his telephone number: 280336. It is the actor's date of birth - 28th march 1936.
Role of the retired opera singer Mr. Bílek was originally offered to actor and writer Jan Werich. Unfortunatelly, Werich had to refuse because of his deteriorating health condition. For his substitute Karel Kalas, who really was retired opera singer, Mr. Bílek was his first and last non-opera film role.