There's a part in the New Testament, a bit before Jesus actually goes to Jerusalem to die, but once he's already got his life's work well underway, where he goes up a mountain with three guys who weren't understanding what was going on. The three guys take a nap. Like he's getting ready to meet somebody out of the ordinary, his face and looks change and his clothes start glowing brilliantly. Then Moses and Elijah (one long dead, and the other rather mysteriously caught up to be with God without dying properly at all) meet him there, likewise "in glory" (i.e. shining).
The three have a chat and they continue to emit the eerie, majestic light. (This light isn't a revealing of Jesus being God's son, as the other two are shiningly "in glory" as well. It isn't what ghosts look like either, because only one of the gentlemen was dead. It might, however, be what people look like in bodies which can deal with heaven and its people, and with still being around hundreds of years after your first body rotted away just outside of Caanan and so on. Moses' own face (on his old body) had shone with light when he spoke to God in person, and now Jesus in turn shines when he speaks to Moses, who is likewise "in glory.")
This light and the guest stars impress the guys who have just tagged along enough that Simon (renamed Peter) has the nerve to actually interrupt these radiant men talking, just so he can make a stupid religious suggestion about building shrines to the three of them. Rather than being in the moment, and wondering or asking things like, "Why are THOSE two guys here, of all people?" and listening to what they were talking about (Jesus' next moves, including going up to Jerusalem to die, which event Peter handles quite badly when it does occur), Peter gets all religious and wants to show respect to something and to some guys that he doesn't understand, rather than shutting up, listening, thinking and getting more understanding of what was going on.
When he interrupts, he doesn't even do it to ask a question. He proposes a religious thing that he thinks the three tagging along guys should probably do now, rather than talk and listen, as they'd been doing. He wants to have a role, that of showing respect, and in attempting to leap in and play this role, he actually not only shows disrespect, but halts the whole thing.
There were so many things he could have asked them. Like, why Moses? Moses was the guy who spoke to the entire Jewish nation on behalf of God, and was frustrated with them and their stupid religious behaviour (like inventing a system of religious worship (with Mooby the Golden Calf, of all things) which would be easier than actually dealing with a God who they needed to see as part of daily life, and who did things following His own time-line). God was frustrated with the Jewish nation and was offering to get rid of them and give Moses better people to lead. Moses struck a deal with God to give the Jewish people time to figure things out, and asked God to view him, not as the exception to the rule, and the only one to be spared the brunt of God's frustration, but rather, as just a typical representative of the Jewish people. Moses asked God quite forcefully to accept him as this, rather than as the exception which proves the rule. And God did. Moses basically said "Accept them too, or reject me right along with them" and there's really nothing God doesn't do like He doesn't get rid of good people and stuff. This thing Moses had done was just like what Jesus was about to do himself.
Moses could do almost anything, but what did him in in the end was overstating God's now-soothed frustration, and lecturing the people in an angry, judgmental, religious way; once he had already ensured that God wasn't going to be looking at them in that way anymore. That was manipulative, an abuse of his position, and not properly representing God and His true feelings in the matter.
And why Elijah? Elijah had come from God and told people to stop messing around, and that when God spoke it was real, and it was serious, and wasn't just some religious thing. Elijah exposed the religions of the time and their invented gods as fake and ineffectual. He insisted upon dealing only with a God he himself could never have invented, and Who insisted His people deal with reality and His actual personality, and not superstition and religious crap they had invented, mostly based on human personality, weather and animals around them.
Elijah could do almost anything, yet what did him in in the end was that he felt too discouraged, unsupported by his community, and alone to go on. He got depressed. Once he couldn't deal with people and just wanted to go off by himself to be religious in a cave, he was no longer of any use to God, and God took him up to keep him company and give him stuff to do later, once he felt better.
So, why those two guys? They'd both clearly screwed up what Jesus himself was now going to need to do properly. They both had been through and experienced stuff more like what Jesus was himself dealing with than probably anyone else had. So they're perfect guys for him to talk to, and they're putting their heads together and commiserating and planning and sharing, and Peter jumps in and says "Hey! You know what would be good? Let's make three shrines! One for each of you! To commemorate this great event when you guys came here and did this! And there could be a miniseries and a whole bunch of paintings made of the event! We could sell tickets to this holy site!" (I "amplified" that last bit somewhat)
At this point the voice of God Himself actually now has to interrupt the whole thing that Peter has just wrecked and tell him to focus on Jesus and what he was doing, and not do stupid religious stuff. This needed to be said to Peter, to the other guys, and to every one of us who reads the story later, just so there could be no possible way we might think that Peter had a pretty good suggestion, but that we'd understand that no, this would NOT have been good, and that the point of the thing was the actual guys living actual lives, and not the tag-along-guys doing something religious, respectful or worshipful. (Never mind that Peter was planning on worshiping not only the Son of God, but two mere human beings as well, on a pretty much equal footing.) It wasn't about flattery, or ego stroking or anything of that kind. It was about "Ok, so here's what I've been thinking..." and "...So then after I do that, I'll go to Jerusalem, and I guess I'll have to do this other thing because of the Old Testament stuff. Thanks for writing that, by the way..." and so on.
ps: I tried to find a good image to put with this blog entry, but though many, many paintings of the event exist, they all have "Abracadabra Jesus making grandiose gestures and shouting 'Ta Daaaah!' while trying to get a tan from the light shining down on him from on high." Despite the fact that the account in Luke says that Moses and Elijah "appeared in glory" (glowing), they only depict Jesus glowing. Despite the fact that his clothes were what was shining, they paint him standing in a shaft a light from on high. Despite the fact that he is there to talk to those two guys, they paint them gazing at Jesus as he poses on a higher pedestal, looking upwards away from them. And usually, they make Jesus levitate. I'm not sure why. And in every painting, despite the fact that they call the scene "Transfiguration," (which means "face changing to look different") they paint Jesus with the same face and look that they always do in all of their other paintings. I picked the one you see above because at least Jesus isn't levitating. His clothing isn't glowing and he's not transfiguring either, but it almost looks like he's very close to actually looking at or listening to Moses and Elijah.
posters to get printed. My "common errors to avoid" one for 14 year olds now looks like this. 
