Monster Pee

A couple nights ago I came across this scene: Maleia and Haley were sleeping on the same pillow on the same side of the bed. We have them sleeping in a trundle bed, so they already sleep right beside each other, but they are in two separate beds that you push together, but one is stored underneath the other to save space. Anyway, so I noticed that Maleia moved onto Haley's side of the bed with her, so I tried so quietly to move her back onto her side of the bed, but she woke up, looked at me and said, "Mommy, I am sleeping by Haley because a monster peed on my bed." Oh great. She has had a few accidents lately, never at night, but my first thought was that she had peed the bed. I checked her side of the bed and, yes, it was wet, but there was no odor. I was puzzled, yet I didn't want to investigate too much since I frown on checking the authenticity of pee, so I started to take the sheets off just in case when I notice her sippie cup. I pick it up and turn it upside down. We have a leaker. So I take the sheets off and put them in the dryer, put new sheets on her bed, put her in her own bed, and she wakes up in a daze and says, "Thank you mommy. Can you tell the monster not to go potty in my bed anymore." I say, " Honey, it was the sippie cup." "Maleia responds, "Gross. He peed in the sippie cup too?!?" She is so awesome. I had a fun time trying to explain this to her at 1:00 in the morning.