So, I have custom Sims like Justin Bieber, Selena Gomez, Miley Cyrus etc etc all with the lifetime wish of becoming a Vocal Legend and I expect them to do that. But as I'm playing on my Sim, I meet these celebrities and learn that Bieber is a Fire Fighter and Miley is a Professional Athlete. So am I to believe that AI Sims are not capable of becoming singers? Should I just change their wish to becoming a Rock Star or something? Or is there a setting somewhere that I can change to allow them to become singers. Is that even advisable? Would the AI perform their profession correctly? So many questions, could anyone have an answer to them all?!

NRaas SP tends to actually pay attention to the sims' lifetime wishes. So yes, a guy who wants to become a firefighter legend will actually go join that profession, while one who wants to be jack of all trades will quit jobs at the required level and look for a new job.

So, yes, if you want him to stay a singer, it can't hurt to make sure his LTW is just that.

EDIT: I mean you need the Become Vocal Legend wish (normally available only to Divas IIRC), not the Rock Star one. The Rock Star one is for the normal Musician job.

Yeah, I had them set to Vocal Legend wish, but as I was playing I noticed they weren't becoming a singer. Like you see in the picture, Justin Bieber is a Fire Fighter even though his life time wish is to become a Vocal Legend. So I'm wondering if there's some option I need to tick.

Hmm... I can't say I played with NRaas SP much, since it tended to mess with my supernatural types. Still, have you tried disallowing Find Job in the sim options?

The only thing I have changed in the settings is I selected everything for allowed career. I also selected manually select career but that didn't seem to do anything.

You could install Master Controller and select the Sim and then choose Intermediate and Career and Choose Job and the select the appropriate career for them. :P

Or maybe Justin really dreamed of being a fireman when growing up, and found the chance to finally live his dream, while Miley knew true happiness would come from leading the Llamas to victory. But, if you REALLY want to deprive them of such happy, alternate life decisions, then manually assigning them to a career is about your best bet.

However, progression in those careers is not nearly as nicely managed as it is for standard careers, where if they show up for work, they will get promoted sooner or later. The Singer track (and acrobat or magician, in case you wanted to go with Justin's second favorite career when he was a kid) requires management that is guided when active, but even with Twallan's SP, less so for those professions. There was a mod around here that let them give big concerts "unsupervised", but I can't recall if that affected only active sims, or worked for "inactive" sims in those career tracks. Haven't personally played one of the SHT jobs in a very long time, so I can't be of more help on that, but I do know that left to their "own devices", progression as a singer (or acrobat or magician) for an inactive is not the same as one in your controlled household. Unless, of course, you feel like rotating among them to move their careers forward. In which case, if you rotate over and find Justin fixing the alarm bell in the firehouse, you could just make him quit and go get the job you want him in.