Do Bool Prop cheats [ctrl shift c at the same time, then type in 'boolprop testingcheatsenabled true'] shift click on the sim you would like to become pregnant and then keep clicking 'more...' until you find 'Spawn'.
But maybe thats why its so awesome - the idea of two Sims so desperate to Woo Hoo they dont care where they get it on, as long as they can find a place to be alone. You need a Sim with a high inventing skill; just make your inventor Sim continuously invent new products until the Time Machine appears as a result of his or her hard work.
The rest is easy, provided you have two romantically involved Sims nearby: just click on the Time Machine, choose Woo Hoo, and watch the magic (or, rather, science) happen. First of all, Woo Hooing in a Time Machine means your Sims can time travel, and thats awesome.
And whats more scandalous than sneaking away during a tour of City Hall to Woo Hoo with a partner?
Bonus points if one of the lovers is the Leader of the Free World. How to get it on: If Woo Hooing in a tent just isnt exotic enough for you, the sarcophagus, also from World Adventures, gives you yet another choice.
How to get it on: Have two involved Sims go on a date to the local movie theater.