Halo 3: Is Recon/Green Skull Real?

ok, my friend has this friend that has recon. his gamertag is JustCallMedink or EclipseTheGod ( hes has 2 accounts ) so me and my friends how he got recon, then he showed us this video them playing the first mission....they went out the map to NARNIA ( the fields ) and he said u will find a green skull on the trees then u get recon! he didnt show us the full video....so me and my friends went to narnia then i chatted with the recon dude....he said the skull is on the tallest tree....so we found the tallest tree but we cant jump on it! we keep on slipping on each others head! and we are going to do it again in 2 days! before we do it! IS THIS SKULL REAL OR NOT!?