Yea, Namco is well-known to reference many of their other franchises in their games. Ridge Racer is probably the most well-known example, since many names of characters, places, objects, and game titles (Yoshimitsu, Erusia, Arkbird, and DigDug for example) are sponsors used on the cars.
I believe the story is that there is a level in Beautiful Katamari where you collect objects in the 765 Productions offices, with Danketsu playing as the BGM. In the Danketsu music video, each idol has a representative "cousin" of the Prince character from the Katamari games.