I'm holding off adding this.
Want to see what others have to says.
Since they introduced autonomous woohoo, my Sims are very keen for it too but I haven't really seen NPCs do it.
Is it just the Sauna for you or also the bush and bed ?
It has happened during club gathering in beds and saunas, unfortunately I didn't have a bush handy in the local area.
Noticed that when club gatherings are active, sims with no relationship levels almost always agree to woohoo even if they've just met the asking member.
However, once the gathering has ended and the sim is asked a second time, it'll usually be a negative answer due to low relationship levels.
NPC sims only ask another NPC or active sim when the club gathering is active, outside of club gatherings, normal social rules apply.
Edit: Should have mentioned this only occurred during club gatherings when making the original post. I was quite tired. ><
Maybe change the title to Auto-woohoo all the time during club mieetings regardless of relationship or something ?
This one makes me think of it being part of the friendly menu
When you open the Romance tab in the social pie menu, the Woohoo interaction is available (regardless of relationship) with a green thumb next to it, which makes me believe it was incorrectly tagged as a friendly interaction for the autonomy modification which the club system is, in essence.
It irks me a little as I shouldn't have to fear relations being destroyed just because I selected "Be friendly to everyone" during club gatherings. If I wanted that, I'd have specifically set "Be romantic to everyone" or "Woohoo with everyone".
It's by no means gamebreaking as it can be fixed by banning Woohoo or romance interactions in club gatherings, I just think it was a slight error/oversight.
Edit: Seems others are having a similar issue here: http://forums.thesims.com/en_US/discussion/864053/autonomous-woohoo
