The name is an obvious homage and satire of Harry Potter. Nigel, like many other characters in the series, is a geeky sidekick to Mandy who also has a crush on her. In his initial appearance he approved of Mandy's sabotage in Toadblatt's school of sorcery and even took the credit for her misdeeds which included being punished by the Dean.
His latest appearance was in the "Order of the Peanuts" where he stole Grim's scythe (a typical act in Endsville) and used to exact revenge for being expelled, sending many students to another dimension. However for once he got something good as he learned that he was a rich heir and therefore he didn't need to be a wizard.