Many years ago the Standard Oil Company changed its name from ESSO to EXXON. Young people who watch American Pickers will know this. If you're old enough you'll actually remember the public campaign.  For months, the famous "put a tiger in your tank" tiger was pictured on a large sign climbing a stepladder to the top of the local gas station's ESSO sign. With a big smile on his face, the tiger held in his arms the new EXXON sign.  Then one day, Standard Oil stations across America no longer had their old ESSO signs, but new EXXON signs. It was a clever campaign. If the new EXXON signs just showed up one day without any warning everyone would have been confused. "What happened to the ESSO station?," people would have wondered. It took a time of transition. 

In the early church it took time for Jesus' followers to realize that the post-Easter Jesus, the Risen Jesus, was the Jesus they knew in Galilee, but also different in important ways. That's what the resurrection appearances in Matthew, Luke and John are for. They helped those first disciples recognize the post-Easter Jesus.  Before Easter they knew him by the sound of his voice, the muscle of his arm, the stride of his gait. After Easter they would learn to recognize Jesus in new ways.