At the opera, Remus is surprised to find that he is bored out of his mind.
It's the sort of cultured thing that he had expected to enjoy very much, but he's found the actual experience of it to be absolutely dreadful waste of his time and James's money. All he sees is a large number of people singing ridiculously lengthy arias, and the editor in him is twitching, yelling at them all to get to the bloody point because he doesn't need all this embellishment. No one does. Not to mention, his sensitive ears are throbbing from the amount of timpani and brass, and he knows he's flinching at every crescendo and imagines that he will go deaf before the night is over. He soon finds himself wishing that he would go deaf quickly so that he won't have to listen to this horror any longer.
To add further insult to injury, when he turns to Sirius twenty minutes in to suggest they leave (willing to consent to some horrible act of debauchery such as mooning the conductor or kissing the fat lady), he finds Sirius utterly entranced. The boy is absolutely in awe of the exaggerated gestures and theatricality of the production. Remus imagines there is a miniature Sirius in the bigger Sirius's head feverishly taking notes that he will no doubt enact in McGongall's class on Monday.
His hope then hangs on James, feeling that the two of them together should be able to drag Sirius out. And scene-making be damned, Remus just wants to leave and get out of this old suit that makes his neck itch and makes him feel very inadequate sandwiched between the perfectly made tuxedos of his best friends. But when he looks at James, Remus sees he is absorbed with one actress on the stage. She's not very important, and is therefore not the size of a small giant. Remus realizes he has the worst luck in the world when he notices this actress has red hair and does actually bear some resemblance to Lily.
And so Remus sighs and sits back, wondering why he'd ever suggested this damn outing in the first place.