Steven mentions that his sister Hayley was giving the coach a Rod Carew in the parking lot. Rod Carew was a Major League Baseball player for the Minnesota Twins and California Angels in the 1970s and 1980s. In addition to being the only major leaguer to ever be born in a train, he was one of the most prolific hitters of his generation. It should be noted that Steve is using R"od Carew" as rhyming slang for "screw".
I'm always down for as many Stephen Hawking guest spots as they can give us. Flight of the Conchords ruled it. And I'm always a sucker for Krusty, so the B-plot was cool with me too. It's a good start for...22 seasons, so sayeth the Couch Gag.