Sid is initially portrayed as an unlucky virgin who has a crush on his best friend Tony Stonem's girlfriend, Michelle Richardson, although he later realizes that his true feelings are for Cassie Ainsworth. Manipulated by Tony, he is frequently unlucky: losing an expensive amount of weed, getting beaten up by Jal Fazer's brothers, getting urinated on by a dog and a homeless person. He is also at first oblivious to the machinations of his best friend who, aware of Sid's undying adoration of Michelle, exploits it for his amusement. Despite this, he seems, at least in earlier episodes, to idolise Tony, replying to the question 'Is that all you do Sid, hang around with Tony?' with 'pretty much'.
Sid's character is generally supposed to be the nice guy, in contrast to Tony's self-serving egotism. He is extremely loyal towards his friends, including Tony and Anwar, who frequently abuse his loyalty and cause him a great deal of difficulty. Sid's nice guy attitude is quick to win the affections of Cassie, but Sid is oblivious, which leads to him hurting her feelings on numerous occasions. Sid is also very intelligent but underachieves in school because he is easily distracted. When faced with failing his coursework however, Sid is able to write an entire history dissertation in one night. His characterisation is often completed by his choice of clothes, including a bright yellow Mega Dog T-shirt, which includes a button which when pressed produces a Mega Dog catchphrase from a sewn on speaker.
For the most part, Sid is portrayed as having a low self-esteem thus is unable to speak up against anyone. But on the occasions when it is most needed, he shows remarkable strength of character, especially in the episode Sid. When Sid's father fails to prevent his mother leaving, Sid explodes with anger, and although his mother never moves back in permanently, this demonstration of strength improves Sid's relationship with his father in the long run. Also, Sid goes on a 'mission of love' to profess his love to Cassie in the final episode of the first series, and later in the second series where he searches for her in New York.
Sid's profile on E4's official Skins website.