This is a funny experience I had recently. Me and my friend boarded the C2 coach of the 12127 CSTM-PUNE intercity at Thane. We had confirmed tickets, both aisle seats, one each on the end of a 3x2 section. There was one passenger with us who adjusted seats with us and let us have his window. We were naturally pleased. When the TTE came to check, just after TNA, he found that the guy had booked tickets for two people boarding at CSTM, but only one pax had boarded. Turned out, the other one was for his girlfriend, who was to board at KJT, but he had booked her on the same PNR because he wanted their seats together. :P As luck would have it, an old gentleman boarded the train at TNA with a CNF ticket with the same seat number as the guy's missing lady friend. Nobody noticed at...
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first because the seat was vacant. When the TTE checked, he was bamboozled at first to find that two pax had been alloted the same seat on the same day. Then, it came to light that the gentleman had a CNF ticket for 11007 Deccan express, which arrives at TNA half an hour after the ICE and had boarded the wrong train. And, he had the same seat number and coach number as the one that happened to be vacant. The guy tried telling the TTE that his companion would be boarding at KJT, but the TTE refused to listen and awarded the seat to the old man on payment of difference(SF charges, I believe). The girl boarded at KJT and found only one seat left. The guy had to stand till LNL where the train emptied out. The amount of coincidences here are staggering.