There is a flashback of Robin eating and receiving an allergic reaction to lobster. You see her actuality eating crab legs, not lobster.
In Lobster Crawl, Lily and Marshall are upset that Ted has taken baby Marvin to see Santa. In a flash-forward, Ted is dropping off his baby daughter for Lily and Marshall to baby sit and he is wearing a wedding ring. Ted didn't actually marry the mother until after several years and 2 children.