Finally, for some real Hagiography

(St. Josaphat, by a pupil of Hans Schilling of Hagenau, Getty Center) 

Allow me to introduce you to Josaphat, (Greek: Ioasaph, Georgian: Iodasaph, Arabic: Yudasaf, Persian: Bodisav, Sanskrit: Bodhisattva), formerly known as St. Josaphat (day of feast Nov 29th, but kicked out of the Martyrologium Romanum in 2004), also more commonly known as (The) Buddha. 

The story of his life and deeds seems to have entered the Christian sphere around the 10th century, and apparently became quite popular in the middle ages, inspiring many descendant works. Shakespeare borrowed a scene involving three caskets for his Merchant of Venice.

Naturally the legend of Barlaam and Josaphat bears only vague resemblance to the canonical sutras: Josaphat converts to Christianism, becomes a king, then lives in the desert etc. etc. Nevertheless it is suprising that until a few years ago, a devout Catholic could light a candle to Buddha. Marco Polo already commented on the parallel Buddha/Josaphat in his travelogue, as did seafarer Diego do Conto when he was visiting Japan in the 17th century.   

Buddha may be the oddest Christian Saint, but he's in good company, with saints such as St. Tron, St. Adrian, the patron saint of arms dealers, or St Bibiana, the patron saint of hangovers.