"Create a Sim, but set his or her traits all to 0. After beginning play, purchase a chemistry set. Mix a yellow potion and have your Sim drink it.  All of your Sim's traits will now be set to 10." - TEM 

"When you want some one to marry you make a love potion and then ask the person to marry you. NOTE: SIMS MUST BE AT YOUR HOUSE IN THE SAME ROOM!" - Kaillie

"Buy all the holiday-ish looking stuff (xmas tree, cookie plate, etc) for Christmas. Get it all out and put the plate of cookies (downloadable at thesims.com) on a table nearby. Get everyone to bed around 8-9 pm and around midnight, Santa will come over and drop off a present. Some example gifts are a television, chess board, etc." - Blink182f

"When the sad clown comes in your house, make sure the Sims are happy, and having fun. The clown with automatically leave!" - Margie

"If you want to see your Sims naked here's the deal. When the Sims is in the bathtub or the shower or the romantic bed delete it and you will have a naked Sim." - Codi the man

"Buy a heart bed and get two sims to really like each other. Tell one sim to get in and then tell the other to 'play in bed' on the options that pop up when you click the bed. When that sim gets in they will have sex and be really happy!" - Bluntflame