To get around the random emotions of NPCs, there are multiple ways to change the emotions of everyone in the area:
1. Vampires can gain an abilty to do a blast of a chosen emotion to everyone around them (I think other sims can do so too but I can't recall off the top of my head which ones)
2. There are lots of items in build mode which give off emotion moodlets which you can place on lots e.g. adding scientist trophies in the library so everyone is focused or adding VIP buckets in a resurant to make sims flirty. There are also mods which have hidden emotion emmiters if you don't want to have to do anything on lots
3. You can use the satelite dish from the science career (or build mode) to make everyone either happy or angry
4. Since I know sims love to randomly grab drinks, you can brew emotion changing tea with the magic tea pot and they'll end up grabing a cup
There are other options too but those are the main ones which should cover changing the mood of NPCs so they're not looking into mirrors all the time; hope this helps!
