Answer:
Three little letters. A paradox to some. The worse that it is, the better it becomes.
What has four legs during the day; and six or eight during the night?
What goes further the slower it goes?
What do you purposefully put lots of in and on your body, but run away from when you encounter it outside?
What can be measured but not seen?
I am owned by Old McDonald.
Difficult
Animal
Easy
Food
Funny
Kids
Logic
What am I?