The role of Alex was a coveted one, with over 100 kids trying out for the part. Alex D. Linz won the part, beating another child star, Philip Petrie, who had also tried out for the part of Sammy in One Fine Day (1996), a role taken by Alex D. Linz.
The film is completely independent of the original movies. There no mention of Kevin or the MacAllisters. The only link to the original Home Alone (1990) or Home Alone 2: Lost in New York (1992) is the Chicago suburbs, where the original film takes place, Mr. Jernigan getting his region hit by a crowbar and a portion of John Williams' score during the beginning credits.
At one stage the script was considered being filmed as a television pilot, but in the end the studio decided to go ahead and make it as a feature film. The reverse would later happen with Home Alone 4 (2002), which was originally intended to be a stand-alone TV movie, but was restructured during production to serve as a pilot for a TV series that ultimately never went ahead.
The original concept involved Macaulay Culkin's character, Kevin McCallister, returning as a teenager. However, the plan was scrapped as Culkin dropped out of acting three years earlier as he thought he was outgrowing "childish" roles.
The trivia item below may give away important plot points.
The scene in the garage where Jernigan sees a pair of legs dangling out of the storage attic and he pulls on them which are actually the legs of a dummy attached to a lawn mower starter which starts and falls through the door onto Jernigan was derived from the novelization of Home Alone 2: Lost in New York (1992) in which the exact same incident happens to Marv when he's searching the garage for Kevin.