PHILADELPHIA — There’s not a whole lot of mirth in the halls of health care right now. COVID-19 has everybody pretty down, and going for medical tests is never anyone’s idea of a fun time. Pennsylvania Hospital’s Cardiology Department, however, just might be the exception. On any given day, you’re likely to hear chuckles — perhaps even a guffaw or two — emitting from the offices of this Penn Medicine cardiac diagnostic team. And then there are the double-takes. Lots of them. “We’re so used to it, we just laugh it off,” said Bob McKee. “It’s throughout our lives,” said his brother, Tom McKee. T…