A time when I'm green, A time when I'm brown. But both of these times, Cause you to frown. But just in between, For a very short while. I'm perfect and yellow, And cause you to smile. What am I?

Break it and it is better, immediately set and harder to break again.

What do you call an elf that can read a pdf document?

I seem so small, yet hold it all, from keys to lipstick, great and small. I travel close through day and night, a world contained in stylish sight.

I won't make the Muppets reference, that has already been done a lot. I will, however, ask you to name the vessel that holds liquids in chemistry, cold or hot.