Steve: I know. She is in such a bad mood.
Tom: I think I'll just stay away from her today.
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.