Lizzie and Matty

 Lizzie and Matty, two children, were sitting outside a clinic. Lizzie happened to be crying very loudly. 

"Why are you crying?" Matty asked. 

"I came here for a blood test," sobbed Lizzie. 

"So? Are you afraid?" 

"No. For the blood test, they cut my finger." 

As Matty heard this, he immediately began crying profusely. 

Astonished, Lizzie stopped her tears and asked Matty, "Why are you crying now?" 

To which Matty replied, "I came for a urine test!"