Mister Sandman

Mister Sandman is a Fallout 3 and Fallout: New Vegas Perk.

With the Mister Sandman perk, when you are in Sneak mode, you have the option to silently kill any human or ghoul while they're sleeping. All Mister Sandman kills earn bonus XP - which amounts to 50 experience points per kill on any difficulty.

Mister Sandman is performed in sneak mode and by choosing "pickpocket" on an unfortunate sleeping victim. Choosing "pickpocket" pauses the game and brings up a menu with the options to "murder" or "pickpocket". Choose the former to activate the perk. When used, a short murder animation follows with the player character looking around and slitting the victim's throat, accompanied by a cartoony jingly fanfare.

Possession of a knife or other bladed weapon is not necessary to perform a Mister Sandman kill, even though the kill animation shows the deed performed with a combat knife.

Sometimes Mister Sandman victims wake up and cry out before they die, thus alerting nearby characters even with 100 sneak and a Stealth Boy, or high sneak, and the Chinese stealth armor. This may happen due to the "stealth" flag being removed from the player while the Mister Sandman killing is in process, rendering the player "detectable", even to sleeping characters as they somehow can observe you while you are sneaking. Also, some victims even stand up, move around, and complain before the game decides to kill them, also alerting nearby characters. It appears as though hostile characters will always wake up if this perk is used on them, greatly limiting the usefulness of this perk for good karma characters.

Behind the scenes

 * The "sandman" is a folkloric character who puts sand in the eyes of little children, causing the rubbing of the eyes that is a sign of tiredness.

Bugs

 * Prior to patch 1.0.0.15, it was possible to use the perk on children. This would not kill the sleeping child, but the experience would still be gained, allowing for unlimited EXP. The bug returns in Fallout: New Vegas.
 * It is still possible to perform Mr. Sandman kills on Kenny from the Point Lookout add-on and Sally from the Mothership Zeta add-on after patch 1.5.
 * Sometimes, dead victims will still speak when you steal nearby items, scolding you for your theft. There are no consequences for this, though, it's just creepy.
 * The player character will sometimes simply levitate over the victim, with no knife animation playing. The cause of this is unknown, but it seems to always happen after the new patch, even without the Chinese stealth armor.
 * Sometimes during the murder, victims will wake, and alert everyone to your presence.(This happens if you are sneaking)
 * It is possible that while murdering the victim, they will wake, stand up and become hostile towards you, however, they will still die after the murdering animation is complete. It seems that when the character being killed starts attacking the player, no damage will actually be dealt by them.
 * Occasionally, instead of murdering the non-player character with the normal animation, your character may lie down beside them. This happens with a fallen slave in The Mill (expansion: Into the Pitt) who you can choose to heal or "put out of their misery". Choosing to do nothing then Sandman Killing the slave results in the sleeping animation being displayed. The slaver reacts as if you had killed them normally, even if they didn't detect it. This is probably one of the only times in Fallout 3 where the Lone Wanderer can be seen lying with another person. This can also been seen in Fallout: New Vegas with "The Forecaster" in 188 outpost. This can cause freezing.
 * In Fallout: New Vegas, If you attempt to use this perk against someone who gets up from the bed, the animation will still play but if the non-player character is killed by your companions or any other non-player character while you are using the perk, the game will crash. If you want to kill hostile enemies while they are sleeping with the perk, do it alone.
 * In Fallout: New Vegas Occasionally, instead of murdering the non-player character with the normal animation, you character may lie down beside them and/or they will kill them with the animation but the non-player character will sink down into the bed onto the floor or into the ground burying them. This happened with Old Lady Gibson and The Lonesome Drifter.
 * In Fallout: New Vegas, many of the refugees in Bitter Springs can be killed over and over again for unlimited experience.
 * In Fallout: New Vegas non-player characters killed by this perk may fall through the floor making it difficult to loot them before they fall.