The answer first. Then the reasoning.
Every explainer opens with the actual answer in two sentences. Read that and leave, or stay for the version with examples.
Common questions
What is the full form of “I miss you”?
“I miss you” has no full form — it is already a complete English sentence, not an abbreviation of anything. What people usually mean is its short form, which is MU (or M.U.), and the number codes that circulate alongside it: 143, 459 and 831. Those three are all ways of writing “I love you”, not “I miss you”.
What do you call the leader of ducks?
A duck-tator. The joke works on “dictator” — swap the first syllable for “duck” and the word survives almost intact, which is what makes a pun land. You'll also hear mallard-in-chief (from commander-in-chief) and quack-tain (from captain); all three are correct answers to the same riddle, and duck-tator is the one that circulates most.
How do you write a birthday message that doesn't sound generic?
Name one specific thing about the person, wish for something concrete rather than abstract, and end on warmth instead of a sign-off. A wish that does those three things sounds like you wrote it, because you did.