Ted: Robin, this show is so dirty, I don't know whether to hug you, or run a shower for you so you can sit there alone crying and clenching your knees.
Robin: It's just bad camera work okay, Wayne our camera guy he wasn't that great.
Marshall: I don't know, I think he did a pretty good job considering he was probably only using one hand.

During the beaver-song, Jessica turns toward Robin, but when the shot changes, she's facing the other way again, though there's no way she could have tuned back.

We first learned about Robin's past as "Robin Sparkles" in episode 2x09 "Slap Bet", where we saw her first music video Let's Go To The Mall. We saw her second music video Sandcastles in the Sand in episode 3x16 "Sandcastles in the Sand".

Barney: Space Teens... is this a porno?? (gets ready to slap Marshall)

This is a reference to episode 2x09 "Slap Bet" in which Marshall and Barney bet on whether Robin's secret is that she used to do porn. If the answer turned out to be yes, Barney would get to slap Marshall.