As a pilot examiner I get to ask the questions and listen to the answers. Sometimes some of the answers raise an eyebrow or two.....
From a Private pilot applicant when asked about spin recovery procedures:
"I don't need to know that, my airplane isn't approved for spins."
From a CFI Airplane applicant when asked how the carb heat on her C-177RG works:
"Carb heat is electric on this airplane"
From a CFI Instrument applicant when asked how the pitot/static system works:
"Air comes from the pitot tube through the airspeed indicater, the altitmeter then the vertical speed and out the static port"
From a PWK based commercial pilot applicant when ask a Class B question:
"I don't know, I never go near Class B"
From a private pilot applicant when asked which gyros would fail if the vaccum pump failed in his 1975 C-172:
"The turn coordinator, the attitude indicator and the vertical speed indicator"
And from several applicants, What the best way to cure hypoxia?
"Open the windows"
There have been other strange answers to common questions along the way. Does one bad answer end the checkride? Most of the time not. But every examiner is different on this opinion. Most examinerss probe a little more to see if its just a brain fart or a real lack of understanding. I've noticed if I get a strange answer to a question, I'll drop the subject and ask a simular question (or questions) later in the oral. Most of the time the light goes on and we have a good chuckle about the previous answer.