I think I did something wrong last time, the Imaginary Friend never aged up or became alive. I've tried googling to figure out the exact process but there's not much concrete info.

What I did: Sim got IF in the mail, spent some time playing with it as a toddler until I got a message saying "They're becoming special friends". Child aged up, IF didn't. She could still play with it as a doll, but it never came to life. Now she's a teen and it's too late, but her younger brother might have a shot, if I can figure it out.

Is there a specific number of hours needed when Toddler? Should IF be in inventory when he ages up? Does "Play Tea Party" make it come to life?

It's my understanding that the doll needs to be in the toddler's inventory. (which makes sense from the "They have become inseparable" message. Have you ever tried making a real life toddler leave a favorite toy behind?)

Yes, well, what works in the game isn't always what works IRL. Like, have you actually tried taking candy from a baby?

*AHEM* Or so I hear. Not that I'd know anything about it. It was never proven, OK?

I think I had to place out the toy just before the sim had its birthday (to child), and the toy came to life a little bit after the sim aged. According to some screenshots I took, I had placed the toy close by when the child aged up, and the toy came alive just after. But it's been a long while since I played around with sims 3, so I'm not sure if you absolutely have to. I think that if the toy roams about the house when the child grows to teen, it will grow up along with the sim.

Make sure you're using the version that comes in the mail, and not the extracted one that you can place in their inventory - the extracted ones don't seem to work, and I've never managed to make them come alive, but they can play with it. It has to be the toy they rightfully own.

Is the Imaginary Friend supposed to show up in the Relationship bar? I've never had one show up there, no matter how long the previous child played with it. I've got 7 Sims on the lot & 1 butler, maybe the lot's just too full so it won't even start the IF process?

I'm not sure what this means; how do you end up with an extracted version? When it's in the boy's inventory it's named "Roche's Toy", so it's the right one that way.

I have been spending a lot of time on this!

The toddler should spend most of their time crooning to and playing with the imaginary friend. When they're about to become a child, try to put the toy on the floor, but it's okay if you don't, just let the child continue to spend as much time playing with and singing to the toy as possible. It's best if the toy gets to be on the floor when the child is not playing with it, but this is not crucial--the relationship is. I have resorted to cheating the relationship to maximum because they only seem to get to 80% by teenhood even with constant interaction and extended lifespan.

I have never succeeded in finding the rainbow gem. Instead I had a child in the household discover potions on the chemistry table and study logic till he was able to make the imaginary friend potion. Then I had him make several copies of it. This is quite expensive--like 5K simoleons? So I cheated again. Then I discovered that by having the other children focus on befriending their imaginary friends and having that child focus on discovering potions, the relationship between the children was not high enough for him to give the potion to the other children as a gift, so I cheated again to transfer the potion to the inventory of the child with the imaginary friend.

It might be crucial to have the toy on the floor during the transition from child to teen, however.

Then at last after real life weeks of gameplay I was ready to have the teen offer to make her now full-size imaginary friend real, and that was so satisfying! Be warned though the imaginary friend converts to a sim with extreme pudding face and pale skin...I left the first as-is, but the second got a makeover in CAS--nothing too drastic, just some color in his skin and a little tweak to his features so he wouldn't look exactly like the first one. I have three more imaginary friends left in this household to convert, and then I whisk the whole household away to found a new neighborhood based on imaginary friends and aliens mainly!

I mean a downloadable version (I think it was this one I tried).
The one that appears in the child's inventory when they get it in the mail is the correct one.

I think I managed to make the toy alive once, but it's so long ago I can't remember if I really just saw a video of someone doing it. My game decided to mess up at one point, and I lost progress, probably also screenshots.

Don't you have to throw a Tea party for the imaginary friend to grow into an actual Sim?

Not that I know. Not if only children can throw tea parties. The imaginary friend I'd taken pictures of in my game came alive about 6 (real) minutes after the toddler grew up, judging by the time index on the screenshots. According to the pics, the child just managed to give the toy a hug before it became real two (real) minutes later.

I believe this is at least part of the problem. You need a mod that relaxes the 8 sim limit in order for an IF to become real on a full household. From the NRaas collection, that would be Mover. I think maybe Awesome allows for this also? Sounds like you could have dismissed the Butler to see if that would have helped, but that's not a great solution if you were attached to them.

I missed that question--in my game, the Imaginary Friend did not show up on the relationship bar until the child reached the teen stage and the Imaginary Friend had been walking about independently for a bit. However, using Master Controller I was able to check on the relationship and ultimately cheat it to the maximum level, because Imaginary Friends show up as sims in the town population list.

To my knowledge, the imaginary friend cannot become real without an action on the part of the sim. It can become independent and strut around, play, prank, nag, eat--but it is still in a transitional imaginary friend form (larger than a doll, but with a scarecrow shape). When it becomes real, it looks like a regular sim with a normal human sim body, not like a scarecrow.

Toddler plays with it, you get the "special friend" message. Then you play with it as a child, until you get the "come out and play" - which can be just remove it from the child's inventory or a "tea party".

The toy becomes animated, but only the child can see it. It can do stuff, but it isn't "real". To make it real, you need the Imaginary Friend potion from the Chemistry workbench. You can make that at level 9 of the logic skill. You also have to be Best Friends with the Imaginary friend before you can give the Imaginary Friend the potion.

So, start off the toddler with the pegbox. Once at level 3 pegbox, when the toddler ages up to a child and starts reading the 1st Logic book, the child jumps to level 3 logic. Or they can get the Imaginary Friend potion from somewhere else.

Also, read the 3 logic raising children's books to the toddler. I forget the titles.