He annoys Fred Flintstone every time he appears due to that every time he delivers the newspaper (which is made of stone) it ends up hitting Fred on the head and breaking into pieces. Arnold's honesty also tends to drive Fred's patience as he will often speak his mind (albeit in a polite manner) and his thoughts usually greatly annoy Fred as well.
His greatest grievance against Fred was joking that he would one day marry Pebbles Flintstone when they're older, which not only annoyed Fred but gave him one of the worst nightmares of his life in which an imaginary adult Arnold replaced and took over every part of Fred's life, like replacing Fred as foreman at his job, replacing Fred as Barney's best friend, replacing Fred as the Grand Poobah of the Water Buffaloes, replacing Fred as the head of the Flintstones family, and topped it all off by marrying Pebbles much to Fred's horror. Despite having been a nightmare, the dream did little to improve Fred and Arnold's relationship.
Regardless of his questionable skills as a paperboy, Arnold is an excellent pin pong and marble player and he is very good at scrabble and many other activities, and he shows that he is well wiser than Fred is and even though he greatly annoys Fred, Arnold is a very friendly and calm young lad who everyone in town liked except for Fred.
Arnold is short with fair skin, brown hair, and black eyes.
- His age is somewhat unknown, although in the beginning of the second season he was known as being 8 years old.
- Arnold had several different physical appearances, just as Joe Rockhead did.