Two children Johnny and Alex

Two children, Johnny and Alex were sitting outside a clinic.

Alex was crying very loudly.

Johnny: Why are you crying?

Alex: I came here for a blood test.

Johnny: So? Are you afraid?

Alex: No. For the blood test, they cut my finger.

After hearing this Johnny started weeping making Alex feel surprised as well as curious and Alex asked:

Why are you crying now?

Johnny: I came for a urine test!