Speedy Pregnancy
Load "Sims 2" and navigate to the house of the female sim you wish to become pregnant. Click a telephone and have your sim invite a male sim to her house. Enable cheats by pressing "Ctrl," "Shift" and "C" at the same time. Type "boolprop testingcheatsenabled true" and press "Enter" when the cheat box appears. Press "Shift" and click your female sim at the same time. Select "Tombstone of L and D." Have your female sim use the tombstone after the male sim arrives. Select the option "Make Pregnant With..." and select the male sim. Your female sim will now be pregnant without having to try repeatedly. You can use this cheat after each baby is born until you have as many babies as you like.
Twins
Follow the instructions in the "Speedy Pregnancy" section. Press "Ctrl," "Shift" and "C" at the same time to open the cheat box when your female sim is giving birth. Type "twinzr2cute" or "twinsr2cute" and press "Enter." Your sim will give birth to twins. Note that this cheat does not work when giving birth to alien or vampire babies. You can also use this cheat without using the "Speedy Pregnancy" cheat; simply wait for your sim to give birth and enter the code into the cheat box.
Alien Babies
Purchase the most expensive telescope, the "FarStar E3 Telescope." Select a male sim and then click the telescope at night to have your sim use it. There is a 4 percent chance each time your sim uses the telescope at night that he will be abducted by aliens and become pregnant with an alien baby. Note that this only works with male sims. This is the only way in "Sims 2" that a male sim can become pregnant.
Vampire Babies
Have your female sim visit the "Red's 50's" diner in the downtown neighborhood. Locate a vampire and build a relationship with him by talking, flirting and otherwise interacting with him. Have your sim return home. Use the telephone and invite the vampire to your sim's house. Use the cheat listed in the "Speedy Pregnancy" section to become pregnant by the vampire sim. The baby produced by your sim and the vampire has a 50 percent chance of being a vampire baby. Alternatively, open the cheat box, type "boolprop testingcheatsenabled true" and press "Enter." Press "Shift" and click your sim. Click "More" until you see the "Make Vampire" option. Make your character a vampire, then use the cheat listed in the "Speedy Pregnancy" section to have your vampire sim become pregnant by the visiting vampire sim. The baby produced by two vampires has a 100 percent chance of being a baby vampire. You must have the "Nightlife" expansion pack installed in order to create vampire babies.