Blackdog22, you are not alone in your thinking, in fact there is a theory for a fill in for Jesus:
Mark 15:
6 Now at the festival he used to release a prisoner for them, anyone for whom they asked. 7 Now a man called Barabbas was in prison with the rebels who had committed murder during the insurrection. 8 So the crowd came and began to ask Pilate to do for them according to his custom. 9 Then he answered them, 'Do you want me to release for you the King of the Jews?' 10 For he realized that it was out of jealousy that the chief priests had handed him over. 11 But the chief priests stirred up the crowd to have him release Barabbas for them instead. 12 Pilate spoke to them again, 'Then what do you wish me to do with the the King of the Jews?' 13 They shouted back, 'Crucify him!' 14 Pilate asked them, 'Why, what evil has he done?' But they shouted all the more, 'Crucify him!' 15 So Pilate, wishing to satisfy the crowd, released Barabbas for them; and after flogging Jesus, he handed him over to be crucified.
"This passage is quite interesting, because it is here that many threads of the story are drawn together. Here Pilate is portrayed as a just and caring ruler, while the Jews are portrayed as an unjust, bloodthirsty, mob. All of the elements of the story so far that have presented various failings of Jews are put into a direct comparison here between Jews and Gentiles, and the story clearly depicts the Gentiles as the good and just ones and the Jews as the unjust transgressors.
There are other elements of interest as well. Line 6 talks about a tradition of releasing a prisoner during the Passover festival, but such a practice is not recorded anywhere else and is highly unlikely, because even holding executions during the holy festival would have been against Jewish law, so they would not have had occasion to release prisoners prior to an execution during the Passover festival because they didn't hold executions during the Passover festival in the first place.
The point of the story-element, however, is not lost on the reader. It is interesting to note that Barabbas literally means "son of the Father". As we have discussed, "Abba" means Father in Aramaic, and bar means "son of". In fact, the original text of Mark may have called Barabbas "Jesus Barabbas", not simply Barabbas. Thus, the two men on trial were not Jesus and Barabbas, but two men, both known as "Jesus Barabbas". Such a reading is not preserved in any of the extant Gospel texts, but there are several 2nd and 3rd century third-party references to the use of "Jesus Barabbas" in this context, and this is, in part, where the tradition developed which claimed that Jesus wasn't crucified, but instead a different man was crucified in his place. This is something that was expounded upon in later stories and is a belief of Muslims today. It all stems from this story element, where the author of Mark has the freed man named "Barabbas" or "Jesus Barabbas", thus some readers later believed that "Barabbas" was actually "Jesus Christ" and this developed into a rationalization for how someone could seemingly come back to life. The rationale went that Barabbas was actually Jesus and that the man crucified was someone else, and that really the man who people saw after the crucifixion was Barabbas, who was really Jesus all along, etc. The silly thing about all of this is that the entire rationalization is built on a fictional story line in the first place. At any rate, that is the history behind this alternate belief."
http://www.rationalrevolution.net/articles/gospel_mark.htm