St. Patrick's Day is a holiday character and national stereotype who, along with Cupid, arrives in Lawndale in "Depth Takes A Holiday" searching for Christmas, Guy Fawkes Day, and Halloween, who have escaped from Holiday Island. St. Patrick's Day is described early on as a leprechaun but if so, he's a pretty tall one. As he and Cupid are specifically on the mission, he is presumably one of the more competent holidays; he's the leader of the duo, but gets irritated with Cupid's laid-back, passive nature.
In "Depth Takes A Holiday," St. Patrick's Day was shown to have breath that smells of beer; this was accompanied with a small, visible exhalation of green-colored breath. He mentions that the 'beer-breath' is "congenial"; even more interestingly, St. Patrick's Day mentions that he is not a drinker.
Because he is an Irish holiday, St. Patrick's Day holds a lot of animosity towards Guy Fawkes Day, who is a British one. He once grumbled about being "oppressed for four centuries" - roughly when the Tudor conquest of Ireland occurred, when England (which already officially ruled Ireland) deliberately tried to devastate Gaelic culture and polity - but in the present sense, so he's presumably an Irish Republican and views Northern Ireland as occupied land.
- St Patrick's Day would probably be very upset to find out that many British people celebrate his day (i.e. all of them who like to drink).
- In the Latin American (Mexican) dubbing, he is given an Argentinian accent.
St Patrick's Day has had a surprisingly large amount of fanfic appearances! A number include Cupid.
- "Restrain Jane Lane!" by Nemo Blank, in which he has to assist Cupid near the end (and is revealed to have once been Dionysus)
- "Everything Happens for a Reason by Mahna Mahna, where he follows Cupid's attempts to alter Daria and Tom's relationship
- Acts of Cupidity by Disco 3:16
- "A Hard Days' Night" by TAG, which takes place around the events of the story
- Repeiceing Down the Girl by Morden Gans, involving time travel
- "God Save The Esteem" by Charles RB, where St Patrick's Day and Guy Fawkes have had a bad breakup
- "Write Off Challenge 9, entries by thatLONERchick )"Will Ye Go Lassie, Go?") and Dennis ("Last Dance", also here): "St. Patrick's Day has left Holiday Island Again and is looking for a date to celebrate his holiday with. Who will be the lucky Lawndale lady, and what sorts of misadventures will occur?"]
- St Patrick's Day Valentine by JoeMerl, where they get together
- Éirinn go Blam by SinisterExaggerator, where someone fatally questions his actual Irishness