The first time I ran RL was also the first time I ran D&D... and only the second D&D game I had been in. So everything was pretty new to me. I had this cool ranger I'd built as a nemesis to the party ranger, but he was too strong to throw at them early on, so I grabbed a few monsters out of the MM (I didn't have Denizens of Darkness yet).
So, as 4 of my 5 PCs (they hadn't met the druid yet) were walking through the forest, they got attacked by half a dozen stirges. Exciting, I know, but it was the first time I ever DMed and I was afraid of throwing something too powerful at them. They actually messed up the party fighter pretty bad, as he had some bad luck with his saves.
Lacking a better way to introduce him, I rolled a d6 to see how many rounds it would take the druid to just happen to stumble onto this fight. He came in just as the last stirge was fleeing the rest of the group, and cut it down out of midair, then started
eating it!
I had a weird player.