On the spot monologues?

Depends how you do it and where.

Here in LA many of the homeless people do just that and I wouldn't define it as anything other than sad.

LOL

But seriously if you do it, make sure it's relevant stuff (maybe like George Carlin used to do -- think that was mostly his act) or perhaps with a funny twist to it... If the idea is to get people to like you, remember you, and want you around you need to entertain them kinda like a standup comedian does. Heck I know Robin Williams would do just what you're talking about on set of Mork & Mindy. They had a script -- but he was flying so high he would just wander into set and start spewing all this crazy but funny stuff (while filming) which is what you see when you watch the show... Part of why you had the genuine reactions from the actors cause they totally didn't know where he was going and had never heard any of this stuff before.... It worked for him... But I think it's also a skill -- you need to know how to make it funny...

I'm sure with a little practice you'll be having them eating out of your hands LOL!

Read the book bossypants. It follows the career of a very successful woman who excelled at just that.