My name can have any letter of the alphabet, but I always have 2 X's

Question: My name can have any letter of the alphabet, but I always have 2 X's.

What am I?

Question: What do you call a sad bird?

Question: Where do all the letters sleep?

Question: What tastes better than it smells?

Question: What goes in the water black and comes out red?

Question: What loses its head in the morning and gets it back at night?