BURBANK, Calif. - A friendly game of word association with Mitt Romney got big laughs on "The Tonight Show with Jay Leno," when the presidential hopeful described his chief GOP rival Sen. Rick Santorum as "press secretary."

The game came after Leno, who didn't believe Romney when he said he hasn't put a "list together" for his vice presidential choices, proposed the back and forth.

"Not even like with the wife?" Leno challenged Romney. "You know, 'Honey, this guy?' Really? It's never come up? I'm not even running and I discuss it with my wife. You haven't thought of, geez…"

"I'll tell you what. I can do you a favor with this. I'll choose David Letterman. We can help us both out," Romney suggested, a nod to the longtime ratings war between the two late night programs.

But Romney wasn't getting off that easy, Leno launching into the game and quickly laying the ground rules: Leno provides Romney a list of candidates and Romney uses one word to describe them.

"A couple of words, maybe?" Romney requested, upon hearing the requirements.

When Leno offered up Santorum's name, Romney responded, "Um, press secretary."

Romney was seemingly referencing Santorum's heated confrontation with New York Times reporter Jeff Zeleny, during which Santorum cursed at the reporter. Leno had mentioned the incident during his opening monologue, which Romney was able to watch backstage, the host joking that he had tried to book Santorum for the show but the censors wouldn't allow it because of his bad language.

As for the other candidates and words Romney used to describe them, Romney said South Carolina Gov. Nikki Haley is "energetic," Florida Sen. Marco Rubio is an "American leader," U.S. Rep. Paul Ryan is "creative" and Donald Trump "huge."

Asked about New Jersey Governor and backer Chris Christie, Romney said he is "indomitable."

"He's a man of strong will. Great strength. Indomitable," Romney said.

Leno, trying to bait Romney, added, "Man of girth."

"Well, if you attack Chris Christie, you're going to get more than you bargained for. He's comes back hard, strong. Indomitable," Romney said, ignoring Leno's jab at Christie's weight.

Santorum was asked about this on the rope line in Janesville. At first he shook his head several times before eventually saying, "Someone needs to work on his jokes."