"She's the most adorable little cookie you've ever seen," the actor-screenwriter says of Sophie, a 3-month-old boxer-pitbull mix. "She looks like she just smoked an exploding cigar."
Theroux and Aniston, 43, became romantic shooting "Wanderlust" in Georgia last fall, but the actor remains reluctant to open up about the relationship.
"I understand the curiosity, but other than saying I am happy, I am not going to indulge it," he tells the mag. "That's building your own torture device."
Of his increased celebrity as beau to one of the most famous women in the world? "[It's like] having shoes that are slightly too heavy—it can slow you down and make you more cautious," he says.
In "Wanderlust," Theroux stars opposite on-screen couple Aniston and Paul Rudd, playing Seth, the leader of a free-love commune in rural Georgia.
"I was thinking of him as a David Koresh-type figure, a comic cult leader who is so sincere in his insincerity," Theroux says of the role. "It's hard to play that douche-y a guy without cracking yourself up."
MORE FROM WONDERWALL:
- Feb. 21, 2017 Blue Ivy Carter rocks an $1800 dress, plus more news
- Feb. 13, 2017 Count down Nicolas Cage's top movie moments