Headcrabs

Headcrabs are minor antagonists in Stealing the Diamond during the Crowbar fail.

Once Henry attempts to pick up the crowbar, a swarm of headcrabs plop onto him, leading to his presumed death.

Trivia

 * The headcrabs are a reference to the eponymous creature from the Half-Life series. They are fragile and agile parasites capable of turning their victims into grotesque, mindless zombies via brute force and mental manipulation.
 * The fact that they appear alongside with the Crowbar refers to how it was commonly used to ward them off in Half-Life.