Ep 21. Father, Son and Holy Guest-Star

In the season 16 episode 21 of The Simpsons, titled "Father, Son and Holy Guest-Star," the Simpson family attends church, where they meet Father Sean, a cool and charismatic priest played by actor Liam Neeson.

Bart is immediately drawn to Father Sean and decides to convert to Catholicism, much to the chagrin of Marge, who is hesitant about her son's newfound faith. Meanwhile, Homer becomes jealous of the attention Bart is receiving from the priest and decides to seek his own spiritual guidance by joining the local group of Wiccans.

As Bart becomes more involved in the Catholic Church, he starts to clash with his Protestant grandfather, Grampa Simpson, who is determined to convert him back to his own religion. This leads to a hilarious and unforgettable showdown between the two religions, complete with a rap battle and a wrestling match.

Throughout the episode, there are also several memorable cameos from other famous Irish celebrities, including U2 and Sinead O'Connor. And as always, the episode is filled with the classic humor and irreverence that has made The Simpsons a beloved cultural staple for over 30 years.