18 wheeler next to a Mini Cooper
First, Fred would cause Maxine a stroke by being unfailingly polite, while she would likely be frothing at the mouth.
Second, though I like your analogy, the Mini is too classy a car and the 18 wheeler too brutish for my take on these two. Think, instead, a Clydesdale next to a wharf rat.
Perfect! Fred's definitely a big, strong, handsome, authentic stallion ........... ;)