Final answer:
The missing letter that completes the word 'J,P,Y_um' is 'I'. The word being referred to is 'JUMP', relating to a baby pig because piglets are often associated with playful behavior such as jumping.
Step-by-step explanation:
The missing letter that completes the word 'J,P,Y_um' is 'I'. The word being referred to is 'JUMP', relating to a baby pig because piglets are often associated with playful behavior such as jumping.