I had an incident where my toddler grew up smartmilk'd and got an IQ of 369 instead of the usual 300 (as shown in the Lot Debugger).
This never happened before, so I labeled him the neighborhood genius.
If my game resets with this mod intact, will his IQ reverse back to 300?
Yeah, you can achieve an IQ over 400 if you "nuke" the toddler, as Pescado says. The method is to force feed the kid five bottles of smart milk in a row, whether the kid is hungry or not. I've been lucky and the high IQ has always stuck on the first nuking, but I've heard that sometimes you need to repeat this process for the smartness to "stick". Also, if you feed the kid another bottle of smart milk once the nuking is over then the toddler will most likely be reset to normal intelligence again. I think that many MATY-ites nuke immediately on age-up and then feed the kid normal milk for the rest of toddlerhood.