What’s served in Halifax with plenty of mayonnaise and is as popular as the iPad 2? (Popular for a few hours this past Wednesday, that is.) Canadian Twitter users were somewhat perplexed to see the McLobster — sold at McDonald’s restaurants in the Maritimes and New England — mysteriously become a hot topic on the internet. Some U.S. tweeters, thinking it was a new product, wanted to know when it would “launch.” (McDonald’s is famous for tailoring its menu to regional tastes. The Filet-O-Fish was introduced to appeal to Cincinnati-area Roman Catholic diners who abstained from meat on Fridays and...