A McMoron is a person who works in a box and hears you say, "I'll have two Big Macs, an order of fries and a vanilla shake." Yet, they hand you a bag containing a Filet of Fish, an apple pie and a sweet tea.
A hardo is a person who tries extremely hard at everything. Most times a hardo will try very hard at things that do not require excessive effort. For example, sports practices, gym class, etc.
Wow did you see Jack at practice today? What a hardo!