My experience was that boisterous shenanigans, like juggling testicles or something, would absolutely not have been tolerated. Indeed, the mood was somber/busin

My experience was that boisterous shenanigans, like juggling testicles or something, would absolutely not have been tolerated. Indeed, the mood was somber/business-like enough that no one even dared. On the other hand, a whispered inoffensive remark to your lab partner would be okay. Something this like this would probably be okay: -- "Be careful not to nick the nerve as you <whatever>" -- "Opps! Better now? -- "Yes. In fairness, it's not her biggest problem right now"