It then goes through every room in your vault, and adds that room to the deck "merge level * stranger chance" times. Normally pets don't stack, it only uses the highest bonus and ignores others. It seems that it increases the chance of the stranger appearing in a specific room, at least from what I have seen. A mysterious stranger gives a hat every time you click on it. If you have a 2.5x pet in that room, it's added 7.5 (rounded up so 8) times. as for the best pets i would say those are the child specials, twin chance, wasteland return speed, damage, training time, objective completion (if it does what i think it does) and crafting time (including the pet which does crafting time and cost at the same time). But like all great games, Fallout Shelter keeps getting better with each new update. Longer explanation: when deciding where to spawn the stranger, the game makes an empty "deck". There is no specific way on how. A fully merged 3 cell room will be added to the deck 3 times. The Mysterious Stranger randomly spawns and when you find him, you get some extra bottle caps. One recent update added a new feature, and that’s the ability to buy, keep, and take care of pets, and the latest one has built on this, introducing a new type of pet for you to unlock. Some receive 50 to 300, while others collect from 2000 to 10,000. It could be a room effect though, in which case you could put one in each room. I've got two and have done that actually just in case (my top two rooms). and stranger chance may be good, but i dont know what it does. I think it's a vault wide effect, meaning only one will work. Fallout Shelter. You have to be quick though as the Mysterious stranger only stays for about 5 to 7 seconds. In Fallout Shelter, there is no set time or required vault size. Mysterious Fallout Stranger Wiki Fando Fallout Shelter Mysterious Stranger Cheat 1) Increase almost all methods. I'm unsure how the stranger chance pet works though. Fallout Shelter Mysterious Stranger Chance Rewards.