Foolin' Around
We see Gerry pretending to play guitar with a stick on the roof of a building in Belfast while they steal scrap metal. He's just being a free spirit as he desires to express himself in this rebellious way. The irony is that because of his carelessness he's mistaken as a sniper and the soldiers begin to shoot at him, which incites a riot within the town and creating a dangerous scene for all those living in the city.
Cross
Gerry wears a cross around his neck in the beginning of the film. His family is Catholic and he tells his parents he is going to mass every Sunday while in London. The irony is that though he wears the cross he lives a lifestyle that is only interested in free love, drugs and doing anything he can to rebel against his father and everyone in Belfast who is at war with his idea of freedom.
Respect
Giuseppe tells Gerry to have some respect after he gets him out of having his knee shot through by the IRA. Gerry believes he's talking about having respect for his dad and his family but ironically Giuseppe is talking about having respect for himself as a man and a human being.
Go Live
Gerry's father sends him to London on a ship so that he has the opportunity to live rather than getting killed by the IRA for being foolish and rebellious in Belfast. Gerry does what his father says, but ironically living to Gerry doesn't equal making a life, but finding free love and drugs. Quite the opposite to what his father hopes for him.
London
London is meant to represent freedom for Gerry as he is able to leave war torn Belfast where bombings occur on a near daily basis. Ironically, as Gerry arrives in London there are IRA planted bombs that begin to go off, and London seems to become a version of Belfast that Gerry didn't expect it to be.
