When I was at Eurogamer's booth, a few times I heard people shouting about MediEval 1, and mimicking Parappa's catchphrase to each other. Sweet Bot also raised a few too.
These were of course shadowed by all the people who got any of Jak's supers. Seriously, twice I heard someone shouting about Light Jak, and my friend almost deafened me when he saw Dark Jak (BTW, that move is awesome. Without even knowing about the move, he got two kills, one of which was me on the other side of the runway on Stowaways)