At the end of Katamari Forever, The King, always so demanding and critical of his son, helps The Prince with defeating Roboking.
The final cutscene of We Love Katamari has multiple endings, all which show the King doting on his newborn son, the Prince. Highlights include:
Three of the endings show the King playing peek-a-boo with Prince, playfully tossing Prince in the air, and singing "Rock-a-Bye Baby" to him, respectfully
The King thanking his son for being born, as the Emperor's approving face appears in the sky above them
The King trying to comfort a crying Prince, saying that smiling will make him "popular with the ladies"
In multiple endings, the King hopes that Prince will become big and strong, like the sun
The King says "This is how We feel about you, little prince," and presses a button; this causes a picture of Prince's face to appear in the stars, along with a message: We Love You.
The ending credits of the first game, especially due to the lyrics of "Katamari Of Love." The second game provides this with the post-credits, final cutscene depicting the the newborn Prince with his parents.