The One In Massapequa - S8-E18
Corrected entry: In the one with Ross and Monica's parents' 35th wedding anniversary, when the parents are talking to Ross and Rachel, there is a picture of the parents in the background, in exactly the same location, wearing exactly the same clothes. That photo would have had to be taken, printed, and blown up in the last hour. (00:05:40)
Correction: Not out of the question. At my prom last year we had our photographs taken as we arrived and then they were available (ie, printed) to buy not much later on in the evening. I imagine that if this is possible, so is the provision of an enlarged version. Added to that, Jack and Judy could very likely have been at the function early, sorting things out, and had the pictures taken then - they would have been wearing the same clothes, and the photographs could have been printed even before the guests arrived.
He's My Brother