I had a couple of sims in Egypt and when they reached their level 3 visa and were able to purchase a vacation home, they bought the one that has all the traps in the basement. Well you know how that basement has a mummy down on the very lowest floor? I guess I was bored that night and decided to try something different just for laughs. When my sim released the mummy, I paused the game and then picked up the mummy and its sarcophagus and carried it to a spare bedroom up in the house. Then I decided to go ahead and get a second mummy and put that one in there too. I wanted to see if I could have my sims make friends with the mummies and have them as housemates.
Well it was pretty funny! The mummies just walked around and didn't know what to do with themselves. At one point, I even put a small bistro table in the room and had my sim make some food and put a plate of food in there to see if the mummies would eat. (they didn't) Then my sim went into the room and got in a fight with one of them and killed the mummy. Then she walked out of the room and had the disgusted moodlet from "rude houseguests!" LMAO!!
Anyway, apparently you can't make friends with the tomb mummies....but it was fun for a laugh.