This was an accident, not a practical joke, but funny nonetheless. My sister works as a medical assistant in a surgeon’s office. Occasionally she calls patients to go over pre-surgery instructions. One patient she called recently was an elderly woman. My sister went over all the instructions with her and at the conclusion of the call wanted to remind the patient to arrive early so the nurses would have time to prep her.  

As my sister spoke, she was thinking 'prepare' and 'prep' at the same time. She accidentally said to the patient, "Ma'am please arrives one hour early for PRAYER." Before my sister had a chance to correct herself, the elderly patient had a shaky reply, "Ooh..my."