I, personally, have never had a run in with a celebrity, but this story that was told on the Tonite Show to Jimmy Fallon and I think that it was pretty funny. Keep in mind the customs agent was an older gentleman and I get the impression that his is the curmudgeonly grandfather type. John Krasinski from the Office, and many other movies such as 13 Hours and the newly released A Quiet Place was on his way to London to visit his wife, who is also an actress.
After getting off the plane at Heathrow Airport, Mr. Krasinski was at the customs desk going through the arrival process when the customs agent asked what his business was in London. Naturally John answered that he was there to visit his wife, who was working on a movie. The customs agent asked if John was also an actor. To this John replied yes. The customs agent asked what Mr. Kransinski has been in and naturally John said one show was the American version of the Office. The customs agent did not look thrilled. He then asked John who his wife is. Mr. Krasinski stated that his wife was actress Emily Blunt. The customs agent looked shocked and upset. He angrily repeated the word “you” a couple of times and then stamped the passport so hard Mr. Krasinski was shocked. Goes to show you that you cannot please everyone no matter how you try.