Some fun Irish sayings are "may the road rise up to meet you" and "two people shorten the road," which are expressions wishing good fortune on others. A fun insult such as "acting a maggot" is an Irish way of saying that someone is being annoying.
Insults and curses are more wordy and detailed in Irish speech than in American English, allowing for creative and silly tongue twisters such a "may you be afflicted with itching without the benefit of scratching."
"That one suffers from a double-dose of original sin" is a saying that means a child is particularly mischievous, and it is a reference to the Christian belief that all people are born with a piece of Adam and Eve's sin of disobeying God's orders in the Garden of Eden. Christian religious references make frequent appearances in Irish blessings and insults alike.