My co-irker is a lousy planner. When he needs help during an experiment he never asks until the last minute. And my boss assumes co-irker takes care of his need for help the way I do mine. ( I send out emails minimum two weeks ahead of time)
So today good coworker mentions that co-irker (who just came back from a spur of the moment vacation) is running an experiment tomorrow. I tell GC that I'm really busy tomorrow, but that I haven't been asked to help. I leave at 3:30 and co-irker disappeared at noon only to reappear at 3pm frantic to get things ready for tomorrow.
The experiment involves a time point, a six hour incubation, and then a 2-3 hour experiment. Co-irker asked me if I can help at 3pm tomorrow. I told him that wouldn't be possible. I"ll be repeating with my boss when he wonders why I"m leaving tomorrow at 3:30 when they're knee deep in the experiment.