Yes, ER is shamelessly incident-studded and catastrophe-driven, with mid-season cliffhangers the rule and doctors getting beat up in the bathroom almost as often as explosions rock the reception area. But last night’s chopper disaster was acutely observed, through characters old and new, in tiny moments that told you that Ol’ Bullet-head was a goner. Favorite touch: Romano’s final elevator ride up with med student Neela Rasgotra to the sound of muzak playing Tom Petty’s “Freefallin’” (EERILY well-suited to muzak). Sure, Romano was a bastard, through-and-through. And yet he was oddly self-conscious, and the writers made him sympathetic at many key moments: in advising Lizzie on whether to reunite with Mark, who by then was dying of brain cancer; in his epic struggle as a surgeon who knew his faults yet knew he didn’t deserve a prosthetic arm. Talk about toying with the audience’s sympathies. Paul McCrane brought a wicked humor to the workday asshole repeatedly redeemed by his superior knowledge of science. In fact, he was about as sympathetic as his more “heroic” colleagues are flawed: think of Carrie Weaver’s self-righteousness and will to political power; John Carter’s denial and numbing sense of entitlement; Pratt’s scrappy machismo; Susan Lewis’s tendency to laugh it up in Vegas and come home married. Second favorite touch: that stoned intern, watching it all from his own private little hell. Third favorite touch: any scene involving Linda Cardellini as Nurse/mother/newcomer Samantha Taggart.