Is it bad or helpful to do some stretches for the affected muscles, grab one's dumbbells from the corner, do a set of curls, squats, etc., set them down, stretch the affected muscles again, and go back to one's business when one has a few spare moments, such as right before leaving for work or some other time when one is not going to go through one's whole routine? Is it better just to have a planned, set schedule for when one will weight train and not touch one's weights outside of those times, or, perhaps given some ground rules to prevent overtraining or injury, can it be helpful to do a quick set here and there during one's day, especially if one has a busy schedule?

is one married to the queen
do it whenever you can,at least you are doing it,but warm up dont stretch(static).

Yes, actually. She's not one of those "my hubby needs a six-pack" wives. I don't think she'd love me less if I was getting less fit rather than more fit. (And I really mean that. I think there are a lot of people out there who say they love their spouse's bodies as they are because that sounds nice, but the sincerely but secretly hope that their spouses would awesomify their bodies.) And when I do curls or push-ups or whatever and she's around, it is virtually always because I want to be doing them. Even so, I like having an audience.

Is this in addition to a normal set routine?

The only way to see real results is though consistent workouts. If your just doing an exercise here and an exercise there, your missing out on the routine as a whole. You need to tell your body that there is more physical work for it to do and it needs to build muscle to handle all that added work. If you don't have at least a minimal pattern, your body might not get the hint.