To start with, anyway.

He just sat there for about 15 seconds, trying to process.

His dick, of course, had access to a faster processing system, at least for certain inputs.

It throbbed heavily, drawing his attention. There was a bulge in his pants leg, clearly visible at the approximate end of his dick.

"Welp, it's either take my pants off, or they're going to be damp anyway", he thought. Some part of him was screaming that this was probably a trap, that Barbara would never do this, but the part of his mind connected to no-longer-Mini-Max had taken over at this point.

After years of practice, it knew this scene - Fantasy Barb on the hunt for her next meal of cum. The proper response was to remove any clothing on the lower body, assuming you'd been silly or unlucky enough to be caught wearing pants, and present yourself for sucking.

Halfway through unbuckling his pants, Maximus realized he was, and fumbled the process slightly. A part of him still thought this was an elaborate dream, and the changes to Barbara's appearance and demeanor over the night were enough so she was almost like the fantasy he'd built off her former reality. His fantasy self wouldn't be hesitating to get blown, so why was he? Did he want it to remain a fantasy? Was the small risk that this was a trap worth the larger risk of not getting a blowjob?

No, it wasn't.
He realized he'd unbuckled his belt already, and quickly removed the rest of his lower body garments. At least while sitting his dick wasn't trying to rip his boxers apart, and he tossed them atop his pants, swiveled the chair around, and pretended to casually remove the nearly bursting condom hanging onto the head of his cock for dear life.

Dropping it with a splat into the trash can, he ignored the smell as best he could and waved grandly at his cock, as if to say "have at it".

Surprisingly enough, Barbara did.

Sinking to her knees, she slowly reached out and touched his cock gently, as if making sure it was real. Then she went into a frenzy of caressing and touching, fondling his cock, then his balls, back to his cock, trying to touch every part of it. She was breathing heavily, almost panting, absorbing the smell from his groin and wafting out of the trashcan in a haze of lust.

After about a minute, she settled into a position, straining to get only a quarter of his cock into her mouth, bobbing past his head and running her tongue across it from all angles. Her hands alternated between hefting and fondling his balls and stroking the rest of his cock.

Maximus idly wondered if she'd develop the deepthroat skills of fantasy Barb, everything else seemed to be changing. But WHY? The only constant he could figure was his cum, but why the sudden switch? He wasn't at any of the standard fantasy switch points in life, not even close to puberty, none of that. Just an average overweight guy in his early 30s. But then, he supposed this was his reality now, not a fantasy, and who said reality had to match fiction?

Two days ago, getting distracted from masturbating would have had his cock soft in short order, but no longer. Still as hard as he'd ever imagined a cock could be, he saw Barbara had advanced to the halfway point, head still bobbing, loud slurping and sucking noises bouncing around the office. His massive balls seemed to be swelling even more, apparently eager to get some real work done for a change. He stared down at them in distraction for a few seconds. They must be on par with a softball each at this point, and that wasn't anything even remotely sane. But then, fantasy him had never been about reasonable proportions or anything so quaint.

Come to think of it though, when he'd masturbated before to fantasy Barb, he'd usually cum in minutes at most, and it'd been at least 10 by now. A thrill went through him. Apparently his stamina for such things had also bent towards his imagined self. That could be...really good...but also bad, now that he'd experienced the downsides of stupidly silly amounts of cum. He'd been having to drink more water than he'd ever done before, and probably should have been eating more as well. No wonder he was losing weight, his dick was eating all the reserves to grow or something.

A muffled slurp of frustration came from Barbara, her hands currently massaging his nuts. Apparently she wanted his cum, and he was taking too long for her desires.

Maximus pondered the situation briefly. Or maybe his newly enlarged dick was doing the pondering, he wasn't sure anymore. Either way, there was a decision before them.

Cum now, or hold off to show Barbara who the boss really was, at least when it came to sex.