Shrove Tuesday or Mardi Gras is not an official Catholic Feast but it does have its origins in the change of liturgical seasons. These resources help us to understand its relationship with Catholicism.
Peter Breughel the Younger’s “The Battle of Carnival and Lent” In the foreground, two opposing processions, the one to the left led by the replete figure of Carnival and the one to the right by the haggard figure of Lent, are about to confront each other in a burlesque parody of a joust. Here, on either side of the picture, are feasting and fasting, winter and spring (the trees to the left are leafless, those to the right have leaves), popular jollity and well-ordered charity, the ill-famed tavern and the church as the refuge of the pious soul. Whilst the father’s work was not lacking in humour, the son’s emphasises the encyclopaedic aspect: the many scenes accompanying the “battle” are all ceremonies or customs attached to the rites of carnival and lent, which succeed each other from Epiphany until Easter. One intriguing element for which no satisfactory explanation has yet been found is the fool guiding a couple with a torch in broad daylight in the centre of the composition. The group is walking towards the right, but with its back turned both to Carnival and the viewer. Source: http://www.wga.hu/frames-e.html?/html/b/bruegel/pieter_y/carnival.html
St. Charles Borromeo Church What is Mardi Gras?
The BBC’s Lent page has a section on how Shrove Tuesday is practiced in the United Kingdom.
From the Archdiocese of Sydney we get an Australian perspective on Shrove Tuesday.
Fisheaters article, Shrovetide features the description of Shrove Tuesday, Peter Breughel the Younger’s “The Battle of Carnival and Lent” (see above) and Pancake recipes!
Catholic Straight Answers Fat Tuesday and Questions About Lent
Catholic Online: Mardi Gras and the Catholic Church