In Miss Busy's classroom there are six desks in front of her own. However only five students (Mr. Lazy, Mr. Bump, Mr. Dizzy, Mr. Silly and Mr. Clumsy) come to her school. It is possible that Mr Wrong was intended to be in this episode as Miss Busy's sixth student but at the last minute he was dropped.
This episode might have been the inspiration for the book, Mr. Bump's Guide to DIY.