The actress admits she thought the funnyman was "cute" and was thrilled he'd accepted a regular role on her spooky drama series, but she couldn't believe it when he turned up intoxicated on his first day.
She recalls, "He made me nervous... because I thought he was drunk.
"I actually called the producers and I was like, 'We need to have a conversation... We have a show that's on national television and you have hired a drunk man to come and play a part on the show.'
"He had gone out the night before because he was excited about getting the show and had a good time and he didn't know until he got home that his call (to be on set) was at, like, 6am and so he was still a little drunk."
After forgiving him for that, Kennedy upset his girlfriend early on in their relationship when he made a careless comment about her body.
Hewitt, who has often fought cruel media attacks on her form, was modelling beachwear for her man when a off-the-cuff thought landed him in big trouble.
She explains, "I was very nervous because people had said things and whatever... so I got in the cute bikini position and he comes in... and he goes, 'Hey, my little pear a**'. I was like, 'I'm sorry, what did you just say... Have you ever seen a pear - it starts thin, it gets fat and it doesn't get thin again.' It's not a cute fruit."
But she got the last laugh when she reminded her boyfriend of the song ex-boyfriend John Mayer wrote for her.
She adds, "I'm like, 'The last guy I dated said my body was a wonderland and you come out with pear-ass?'
"But we've worked it out now and we embrace the pear... Now, 2010, it's all about the booty."