Wiktionary
n. Someone or something new to an existing community.
Wikipedia
"New Kid on the Block" is the eighth episode of The Simpsons' fourth season. It originally aired on the Fox network in the United States on November 12, 1992. After meeting his new neighbor, Laura, Bart develops a crush on her, only to later discover that she has a boyfriend, Jimbo Jones, whom he attempts to scare off so that he can have a relationship with Laura. Meanwhile, Homer sues the Sea Captain Horatio McCallister after being kicked out of his all-you-can-eat restaurant while still hungry. It was written by Conan O'Brien and directed by Wes Archer.
Usage examples of "new kid on the block".
At 7:40 the bullpen started filling up with officers grumbling about hangovers, Monday mornings in general and Bucky Bleichert, dancemaster turned puncher, the new kid on the block.
The world, and more important, the Bureau, is watching, and you're the new kid on the block.
They said he may be a new kid on the block, there's a constant flow.
He was supposed to be an undetectable substitute for his brother, and instead was feeling like the new kid on the block.
He might not have any blots on his copybook, but it made him very much the new kid on the block, and he must have realized by now that the rest of the squadron expected their admiral to pitch a tantrum over their recent performance.