Both from the same show.
Act 1: Actor sits on a bar stool.
Actor cannot do this. The blocking requires that the actor approach it by taking a few steps backwards, and inevitably they trip over it or knock it over or slide off of it or, on one memorable occasion, miss it completely, "sit" on thin air, and crash to the ground.
Actor is moved to the sofa instead.
Act 2: Actor perches on arm of sofa while holding a glass of brandy.
Actor cannot sit on arm of sofa. Actor inevitably slides off to one side or the other. (Since the sofa is occupied in this moment, this involves sliding into the lap of a castmate.) Costumes begins to complain about frequency of brandy-spills.
After futive design meeting about possibility of adding velcro to the bottom of actor's pants, change blocking to have actor lean on the bar instead.
I never thought I'd see the day when someone needed help sitting, but there you have it.