Alright, in the episode where the 2nd exam ended during the Chuunin exam, Tenten made a comment on how Kakashi looked like compared to Gai.
In episode 100 (I think, the one devoted to Rock Lee's past), the Genins were watching Gai and Kakashi fight over rock-scissors-paper. I doubt the team can easily forget who Kakashi is since he's Gai's "eternal rival".

To me, the rock-scissors-paper incident happened before the Chuunin exam, but Tenten's comment during the exam made it seem like she saw Kakashi for the first time. Anyone got an explanation for this or did the animators screw up?