"Honestly, I haven't seen any of her movies and know nothing, really, about her work," the American Idol castoff revealed during a recent radio interview on KOST 103.5 FM's morning show.
"She's super cool, man," McDonald, 26, added. "I think she likes me more because I've never seen any of her stuff."
The singer also admitted that when they first met at a movie premiere for Red Riding Hood, he didn't know who Reed, 22, was when she introduced herself on the red carpet.
"She came up to me and was like 'Ah, you're great.' And I was like, 'Awesome, thanks. You're cool, too,' " he said with a laugh of his girlfriend, who plays vampire Rosalie Hale in the popular movie series.
But since that meeting, the two stars have managed to find time to "hang out" despite their busy schedules.
Just don't expect McDonald to rush out and rent his gal's movies. "I'm not watching any Twilight movies," he said. "I'm sorry."