Lancaster played the prank when he pulled Twelvetrees out of breakfast to let him know he had been summoned to join the injury-hit Lions in Australia. Twelvetrees thought he was in trouble when Lancaster tapped him on the shoulder and asked if he had seen his text message, before taking him into a private room.
The Gloucester centre had been due to start for England in their second Test against Argentina. Lancaster said: "I pulled him out and said 'Can I have a word about Saturday? You're not going to play'."
Lancaster continued: "He went 'What have I done?' I said 'You're off to Australia!' It was a bit of a wind-up but a nice wind-up. I am delighted for him. His form in the first Test was excellent. His confidence is high and he is more than capable of going out there and playing well."
Bath centre Kyle Eastmond will make his first England start in Twelvetrees' place with the uncapped Northampton fly-half Stephen Myler promoted onto the bench.
Twelvetrees, who will arrive in Sydney on Friday, is due to play for the Lions against the ACT Brumbies on Tuesday - and Lancaster will see him in Canberra.
The England coach is heading Down Under to catch up with Graham Rowntree and Andy Farrell plus the Lions' red rose contingent, which now number 10.
Twelvetrees was called up to provide additional options because the Lions have picked up a number of short-term injuries in the back division, to the likes of Brian O'Driscoll, George North and Manu Tuilagi.
The call-up to help the Lions beat the Wallabies had special resonance for Twelvetrees because his mother, Beverley, was born in Australia and her family are based in Newcastle, New South Wales.
"They (Australia) can't have him," Lancaster joked. "It's too late - he is capped."
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