Mrs. Sally Phelps thinks Huck is her nephew, Tom Sawyer. She had received a letter from her sister, up north, informing her that Tom was coming south on the steamboat for a visit with his Phelps family relatives, so was anxiously awaiting Tom's arrival. When she sighted Huck, she jumped to conclusions, based on her anticipation.
"It's you, at last!-ain't it?" I out with a "Yes'm," before I thought. She grabbed me and hugged me tight;...and kept saying, "You don't look as much like your mother as I reckoned you would, but law sakes, I don't care for that, I'm so glad to see you! Dear, dear, it does seem like I could eat you up! Childern, it's your cousin Tom!"
Since Huck was the first to arrive, he had the role of Tom already going when he encountered the real Tom Sawyer coming down the road on the way to the Phelps farm. Huck brought Tom up to date regarding the mixed-up identity he had been assigned, and Tom jumps at the chance to have an adventure, as he thought of the joke he hatched to play on the Phelps' family.
Upon his arrival, Tom first introduced himself as William Thompson, of Hicksville, Ohio. During his first dinner with Huck/Tom and the Phelps clan, he reveals his "true" identity as Tom's older brother, Sid.
me and Tom thought it would be a first-rate surprise for him to come here to the house first, and for me to by-and-by tag along and drop in and let on to be a stranger. But it was a mistake, Aunt Sally.
The true identities of Huck and Tom aren't revealed until Tom's Aunt Polly, Sally's sister, arrives on the scene.