Lily grinned her way through James' ramble, rolling her eyes in the appropriate places. If there was one thing she could be sure of in the war, it was that no death eater would be able to a) impersonate, or b) imperio James Potter (or Sirius Black, for that matter). He was just too insane and fantastic. It would be far too exhausting to try and master his mannerisms and modes of speech because there was no method to the madness. He was all over the place. Not to mention that if a death eater polyjuiced as James or an imperio'd James showed up somewhere (like this, for example), it would take any member of the Order three seconds before they figured out what was going on and sent a stunning spell in pseudo-James' direction.
"Hello, everyone," Lily said as James finished up, swotting him playfully on the shoulder. "Sorry we're late, if only by a few minutes. We were up to our eyeballs in flour when your patronus arrived, Edgar. I really wanted some biscuits, you see, and James tried, he really did, but in the end we had to call a truce with the kitchen. Is everything all right?"