I would like to include a note, cause I'm not absolutely sure but as I solved the problem I had in my game, maybe it can be useful. I had the problem with Sims reverting to the CAS manequim face after I build a Sim in CAS. I had this BEFORE Pets so there's another reason for the reverse.
I was using a replacement package I downloaded here and should make all manequim to have a color in BodyShop, instead of the gips grey. I chose the TAN skin as default.
So, it started to revert my created Sims. I use an extreme modified Faces Package and when I made very big modifications on Sims, they reverted to the Manequim Face instead (very boring). The problem stopped when I took out the skin color replacement.
The other movement that causes the reversion in my game is when I create Sims with very thin nose. The thinnest nose belongs to the CAS manequim (in common with the "PointyEars" Archetype) and cause the reversion. So, if I modify a Sim's face and use the "alien" archetype nose, I have many chances to have the reversion again.

get this... I Install pets patch, jewelry, glasses, etc. work fine
BUT now the FACES are flashing blue!!! FACES!!!!!!

Sometimes, deleting the file "Accessories.cache" (located in My Documents\EA Games\The Sims 2) may help. The problems you mention are often related to custom content that is moved away or replaced with new versions.

once there was a stray on my lot and i thought this was really funny:my sims head was a stringy and attached to my mouse and with my custom hair the bangs float and turns green on the edges but once he left it went back to normal O_o

...my sister's game is doing something weird. Her sims look right in-game, but the picture of one of them (above the status bars) has her dog's face. She wanted me to check and see if this was a common issue. So... is it? If it helps, I know she has no cc whatsoever, and the only expansions she's got are Nightlife, OFB, Pets, Apartment Life, and M&G.