I call that a "Stink Grenade"

When you pull into the daycare parking lot and a suspicious odor wafts up to greet you from the backseat....

You have a choice:

Bring the kid in and be totally honest and confess that the kid has crapped his diaper, thereby risking good-natured teasing from the staff as they urge you to change said stinky diaper yourself, which will make you late for work. Again.

OR

Pretend your sense of smell has gone wonky and you don't notice the open sewer scent radiating from your second-born. Kiss him goodbye and wave cheerily as you leave.

Guess which one I chose.
Heh.