"It is a symbol of Irish art. The cracked lookingglass of a servant." -- James Joyce
What Is Going On?
The captions are mildly amusing, but what is going on? My guess is that this is an imitation of some style of conversation they see in their environment, e.g., perhaps the way their parents argue, and that what amuses them is when the other really gets some gesture correct.
But then the leg lifting is left unexplained, because who lifts their leg like that when they argue?