Nitrous Oxide. In the vast majority of cases, with low to moderate doses of nitrous oxide in the dental office, these types of situations do not occur. In higher doses it becomes more common. One of my dentist friends had a police officer who suddenly jumped out of the chair and drew his gun. Scary!
Yes. Some patients do report auditory as well as visual hallucinations with nitrous oxide.
Yes. Many strange sensations have been reported with nitrous oxide gas use. Typically nothing bad, simply out of the ordinary, odd sensations.