To Wake Up On The Wrong Side Of The Bed

Context #1:

Tom: Man!  Chrissy must have woken up on the wrong side of the bed today!

Steve:  I know.  She is in such a bad mood.  

Tom: I think I'll just stay away from her today.

Context #2:

Sara:  Jenny, can I borrow a pen?  I forgot mine.

Jenny: Really? Again? You always forget your pen.  How many times has it been now? A million...

Sara: Wow!  Somebody woke up on the wrong side of the bed.

Jenny: I'm sorry.  Yeah, I'm a little stressed out today.  Here you go.  You can use this pen.

MEANING: to wake up on the wrong side of the bed is an expression used when someone is really grumpy or in a bad mood.  It is almost always used with a past tense form, like in example #2.