Tom Brady -- Reveals Halloween Costume ... Just Call Me 'Barf'

Well, this is the most adorable thing you're going to hear all day -- Tom Brady's 4-year-old son revealing that he and his famous daddy are gonna have matching Halloween costumes.

Tom was having his weekly conversation with Westwood One's Jim Gray on Monday ... when Brady's son Benny grabbed the phone and the cuteness took over.

So what's the big Brady family theme this year?? Hint: it all has to do with a character named "Barf" ... but it's not the guy from "Spaceballs."