a wet blanket (informal)
someone who does or says something that stops other people from enjoying themselves.
I don't want to be a wet blanket, but you really must play your music more quietly or you'll disturb the people next door.
Somehow, a canopy of wet blanket seems to descend upon the company, and Lady Tippins was never known to turn so very greedy or so very cross.
Our Mutual Friend by Dickens, Charles
Its head was covered by the wet blanket and it was NOT SNORING ANY LONGER.
The Original Peter Rabbit Books by Potter, Beatrix
引自碧翠斯波特「彼得兔故事原版」(The Tale of Mr Tod)
It was what Jotham called a sour morning for work, and the horses, shivering and stamping under their wet blankets, seemed to like it as little as the men.
Ethan Frome by Wharton, Edith