Strange beasties that grow out of dolls some Sims are given as babies.
Once a baby Sim turns into a child, the Imaginary Friend can turn into a toy. Other than that, they seem to be normal children as far as a I can tell. I haven't tried the third generation of an Imaginary Friend. I assume their children would still have the Hidden Trait of being able to turn into a toy.
They strut around while in toy form, but you can also have them "strut here" instead of "walk here" when they're in human form.
Once made into a "human" Sim they live as long as a "normal" Sim; they can reproduce with a Sim mate though will not always be able to pass on their IF genes.
Hard to see here, but Lucky took the potion.
The imaginary friend, now real, will have an odd set of clothes and probably coloured hair. Lucky's here, was actually a very dark green.
I didn't notice their needs freezing while they were toys. The toy state is just changing their appearance into an Imaginary Friend. Everyone can still see and interact with them since they're real.
BUG ALERT
Breeding IFs and vampires could be a problem: There are reports from Simmers that breeding a vampire Sim with a former IF caused major game borkage, and wrecked the whole game file. IFs seem to have difficulty when bred with any magical creatures, such as vampires and fairies. They will apparently breed safely with ghosts and mermaids, though.
There are also reported problems when there is more than one imaginary friend doll in the household (even still in the mailbox!). Lags and Error 12.
Opportunity won't fulfil? Is the Science building in your town doubling as a hospital? Delete that lot and and placing separate science and hospital buildings.
There is an Opportunity that asks your Sim to collect a Rainbow Gem and send it to the local Science Lab.
The Science Lab will in turn produce a Potion your Sim can give the Imaginary Friend to turn it "real". This option does not appear for Sims who do not have an IF.
This potion requires the Sim find the Rainbow Gem HIRSELF. Buying a gem, or being given one by another Sim, does not count, and be warned, Rainbow Gems are RARE. They are a base game gem and do spawn in the base game worlds. As far as I can discover, they do NOT spawn at all, EVER! in Isla Paradiso.
This Opportunity is a dreadful time-waster.
By the way, the Alchemists' Potent Cure elixir does not work on imaginary friends to change the lifestate.
If you wish to change your IF into a "real" Sim, you have to totally remove
the IF's occult status first, with MasterController Cheats. THEN an IF can
become a Fairy.
See http://nraas.wikispaces.com/MasterController.
Sita July 16, 2019