The word queue is ironic. It's just q with a bunch of silent letters waiting in line.

Behind the Groan

Four Letters Waiting Behind Q

The word “queue” is pronounced exactly like its first letter, leaving “ueue” silent. A queue is also a line of people waiting their turn, so the unused letters appear to be standing patiently behind Q. Write or show the word if the audience cannot see its spelling. When telling it aloud, say the first sentence normally, then give the second as an observation you have only just noticed. The joke becomes clearest when listeners can picture the letters arranged in order.