Even the Slayer can be felled by the flu. The second season Buffy the Vampire Slayer episode, amusingly titled "Killed by Death", has Buffy landing in the hospital after fainting in the wake of a fight with Angelus. While convalescing, she glimpses one of the creepier monsters on the series, a toothy gentleman called simply "Death" by the kids at the hospital.
As if the flu itself isn't dangerous enough. This demon guy, it turns out, is invisible except to people who have the flu--and it sucks the life out of sick people with its proboscis eyes, leaving bystanders wondering what the hell happened.
There's a lot of potential in this idea--the terrible feeling of a loved one being taken by an unstoppable and unknowable ailment, the physical manifestation of that terrible illness in the form of a truly nightmarish figure. I think the episode could have done a lot more with the idea but I do like Buffy's lifelong fear of hospitals being related to a memory of seeing her cousin fall prey to one of the demons.
Angelus briefly turns up so Xander can confront him. Sometimes, when Angel was a villain, his appearances felt a little superfluous. The Big Bad in each season didn't normally appear in every episode but I suspect since David Boreanaz was in the opening credits the makers of the show were obliged to bring him in regardless of whether or not they needed him. The effect is to somewhat diminish the sense of threat he poses since each confrontation ends with him running away with his tail between his legs.
Twitter Sonnet #1439
The taxing claw discovers ev'ry nose.
The dreams of scattered cookies fell to crumbs.
But something lurks and counts its silver toes.
The sentence works beyond subtracted sums.
The rusty shades concealed a singing voice.
As razor cars were yellow passing by.
Resorting last to straws we slammed the choice.
And now relax beneath a settled sky.
The ground contains decisive little hogs.
A shadow tells the tale of clime and year.
Alarming clicks repeat in temp'ral fogs.
The babe was got before the polka cheer.
The rolling drums entail a demon's name.
The largest house accrues a boat of blame.