I have noticed

[MrsJHolley]

I have actually seen and revived several toon at zero. I have notice that are not true sad til you are -1. Take a look at the toon that are sad on the pg's. If they are freshly there the laff will been -1. However they don't start to get a smile back til they are 1. 0 seems to be the twilight zone. So-to-speak.

Have Fun
Good Luck
MrsJenny

[Pinky]

Toons go sad in battle at zero (normally) but apparently a bug occasionally results in a toon who can go negative and still be tooned up.

Toons sent to the playground always start at -1. It is a timing thing. After the first 30 seconds (or so), you can see the laff meter expand, yet the toon will still be sad. This is when the toon goes from -1 to zero. 30 seconds (or so) later, the toon goes from zero to 1 and becomes happy again, able to get on the trolley or teleport again.

Note, you can shop in the gag shop while sad.

[Sir. Laughalot]

That happened to me once, and I got through the building. Also, one of my pals in a Cog Building got sad, and I toon-uped him.