I was not really sure of the name of this topic but I think this will do.
When experimenting with the mad science career which will unlock the 'experiment on object' ability and which experiments could provide a good moodlet on the sims I've find that placing a few positively experimented gnomes as well as some chairs around the cradle of a baby or toddler can easily make his or her mood ultra happy. Because the total mood of a baby and toddler doesn't raise to the top when the parent takes complete care of it (at least in my game), including the bonus of what a nicely decorated room provide, which still isn't enough to let the lifetime happiness points rolling in, placing the cradle in the 'zone' of some experimented objects can make a toddler already have 10.000 lifetime happiness points when he or she grow up to be a kid, compared with taking enough care of it of course. 10.000 is hard to do, but it will work when you set the bar that decide how long a sim lives to the absolute right.
I couldn't decide on where to put this post (in the Science career part of the forum, or the how to raise a kid part) I place it just here, because I believe it could at something to the site.
I didn't find this on the site myself so I decided to make a post of it. If it still already excist, some moderator can hit the mighty delete button.
Edit: When a experiment turns out to be successful, don't be afraid to do another on the same object. Some experiments give better moodlets than others.
P.s. Sorry for eventually bad spelling. I've checked this post myself 5 times or so, with some translating site but well, for some things I'm still blind. :S
[corrected for spelling - wildredchild]