Sims with very high romance bars can also slip into the closet for a quickie - even if that closet is in a public place, like the local bar.
Sims looking for just a smidge of adventure can try WooHooing in the shower, thanks to The Sims 4: Discover University. Speaking of celebrity Sims, those with a built-in money vault and more than $5000 get a few extra perks, like napping in their money pile or rolling around WooHooing in it with their loved one. Famous Sims also get a special place to sleep because beds are so basic, and they can Woohoo in their futuristic sleep pods. Vampire Sims can enjoy the same features other Sims enjoy in their beds, including WooHoo.
For the most traditional and conservative of Sims, there are plenty of indoor places for WooHoo, the most obvious one being in their bed.