For example, when I asked the question tell me what was the last lecture you attended at the university? I haven't still come across a single person who could answer that question. Most of the people were left kicking their heals on trying to recall the last lecture that they had attended. They can remember only a few lectures they had attended to, in most cases those were exceptional lectures which had an element of surprise or the lecturer had narrated it in a memorable fashion leaving a lasting memory.
Another question I asked was on, what is the last movie you watched? It was a surprise, where a lot of people unintentionally lied to this question, they told the movie which had left a lasting memory than the actual movie they watched last. Its again the case where we forget about a lot of movies we watch since they are without a substance or a story.
Another question was to ask audience which slide they remember from a presentation that was done 10 minutes ago. People mostly remembered the crazy slides or the visually appealing ones which went with the story.
You guys also to try these questions on different people, I assure you that its interesting. btw now I have come to the age old conclusion that to have a lasting memory we need to have a story and element of surprise. Food for thought for all presenters.