Enable an outfit change based on an emotional state?

I would love to see sad Sims suddenly change into sweat pants to mope about the house, or flirty Sims change into ever sexier underwear.

Can it be done? This might motivate me to finally attempt to mod the game myself.

It makes sense that it would be possible. You'd have to make a new interaction to "change into mopey sweatpants", or "change into flirty underwear", then make it only available when the sim is in the right emotional state.

So it wouldn't be possible for the Sim to change outfits by themselves if in a certain emotional state and location (Home?)

I view the world of programming as "anything's possible".

In theory, you'd register your function to fire whenever the sim registers a mood change, and if it's one of the moods you have the outfit enabled for, you could then call some other function to initiate a change of clothes. I myself have not looked into the code for either of those yet, but it certainly would be a place to start.

I have messed around with outfit change data, and I think (although I haven't tested) you can have existing outfit changes test the sims mood with XML tuning alone.
So, for example, one could make a sim go to work in their sleepwear if they are "playful" or shower with their clothes on if they are "embarrassed", etc.
I would have to actually test it out to see if these tunables actually work as advertised. Even if they don't, it is certainly possible with script modding.

Oh gosh. If sad sims moped around in their activewear or flirty sims wandered the house in their sleepwear, that would be amazing.

Tried to do this with a tuning mod, wasn't successful.
I tried to modify the EnterBathing outfit change reason to test the mood, and not change thier outfit if they were embarassed.
The result was that any time the outfit reason change got called, the Sim would reset and not complete the interaction. Probably, an error occurred.
It could easily be that I had a syntax error or didn't write the test tunable correctly, but I didn't have time to look into it further.
It might still be possible with XML tuning, but it is certainly possible with script mods.

The Animal Hats that come with the digital deluxe edition have attached moodlets... there are like 7 flavors.

So yes, it's possible.

There's a thread around here by Snaitf about hijacking the text that goes with that functionality. Study the hats and you will find your answer, I suspect

I think the OP wants the opposite: to have his sims change clothes when their mood changes, not to have the mood change when they change clothes.

Somewhat unrelated, I'm still trying to make the moodlets attached to clothes work. I can make them show in CAS (just have the first entry in the TGI List inside the CASP, the one that is usually zeroed, point to the buff you want to use), but I have yet to find how to make the buff actually appear in game when the sim wears that piece of clothing.

Ohhh sorry misunderstood, thanks for the correction.