What should I do if my dad is seeing and hearing things that are not there during the night?

I"m glad you have a sense of humor! I don't think this is unusual for someone that age - it could be a sensory thing, or he was dreaming. If he starts doing this often, especially when he hasn't been sleeping, then I'd make sure a doctor evaluates him - and his current medications.
Take care - and keep laughing!
Carol

I don't find this unusual either. The key elements are "99 year old" and "got up at 10 pm".

A couple of weeks ago my 105.5 grandmother paged me 4 times during the night. Page #3 involved "2 dogs in the room", while #4 at 5 am involved a woman on a pink motorcycle! (she has way better dreams than I do)

I figure that 2 effects are in play. First, diminished ability to distinguish between dreams and reality, especially immediately upon awakening. And second, maybe the mind compensates for a dull, mostly bedridden existence by creating even richer dreams. Even if that point is incorrect, it's still interesting to see that her dreams are vastly more interesting than her normal routine of ordering me around 24/7. Good for her to have that outlet.

My husbands 98 year old grandma use to get up in the middle of the night saying there were people in her room and in her bed and I would come in and turn on the lights ( not so they were bright but enough to see clearly) and I would say...ok people grams wants to sleep its time for everyone to go! I point to the door then proceed to follow the people out and i walk out and come back to into her. She would look at me and say thanks, and tell me next time tell them they can't stay so late!!

I believe someone might be there too!! Grams always talked about this man that was here with her ( there was no man!!) I think it was her late husband who passed 40 years earlier and she just didn't recognize him!! But all in all you just need to keep your sense of humor!! Its that humor that will help get you though some of the hard times!! Good luck to you and I'll keep you in my prayers!! :)

Lord I know this feeling. My mom gets up sometimes at midnight, one or two and decides its morning even though it is black as pitch outside. What I try to do is head her off prior to her leaving her room and explain very calmly that it is too early and we aren't done sleeping yet so she needs to go back to bed. Most of the time she has already made her bed and sometimes has gotten dress, even then I try to convince her to lay back down for a while. Luckily she usually falls back to sleep.

When this happens to my clients, I just handle the situation. I dismiss the man in the hard hat who informs my lady that someone called in sick. I walk through the hall and re-lock the front door. I make sure all those "people" are gone, and then I assure her that I will keep good watch in the hallway to keep these people out! I listen to the stories (and they ARE fascinating) but quickly move on to other things. It's a great way to practice being an actress. Improv. Good for your brain!

I'd like to add, the worst thing to do is disagree with them, go along with them and try to redirect.

It could be that his senses are up and alert, or that "someone" could have tapped him on the head and told him to get up for lunch. I'll probably seem ridiculous for admitting this, but I kind of believe that there is such a thing as paranormal activity, stuff that happens but can't really be explained. As you said, he wasn't asleep when this happened. Now, I'm not exactly 99 myself (I'm 23, ha) but I have experienced some weird occurrences in my lifetime. When I was a child, I was asleep in bed when all of a sudden, I heard rather loud scratching on my pillow. Of course, I woke up, but the scratching alarmed me, so I just pulled the sheets up over my head and tried to go back to sleep.

My mom does that occassionally and it is usually from a UTI. Get her meds and she is ok. Sometimes she does dream and thinks it is real. Usually my deceased dad is the dream, or my deceased brothers. Maybe they are visiting her. Their deaths have weighed heavily on her.... How knows?

Thanks for the input, I did make a doctors appointment to have him checked out,
See where we go from here.