Has anyone done it? Ever? Probably, yeah, although I can't think of anyone I know who did. I also don't see the utility, unless it's a fellowship you really, really want/can't see yourself being satisfied without. Job generally trumps fellowship, now and for your future, because experience generally trumps fellowship. Generally. But if you really want to do nothing but neuro, or peds, or forensic, or whatever which has nothing to do with your current job offer and which is much harder to do without a fellowship... well, that's up to you. You also -might- find a job willing to take you back again after fellowship, but I really wouldn't hold my breath. Alternatively, if finances permit, you might be able to do locums for the year -- but again, experience tends to trump training and if you have no job experience I suspect very few places are going to want to bring you in to fill a gap as a locum for a few days/weeks/months without some better reason to feel confident you can handle it.