Dave Coulier is one of the celebrities insisting Robin Daggers' song isn't about him, asking why they always assume it's him. This is a reference to the rumor that Alanis Morissette's "You Oughta Know" was about him.
When Dave Coulier says "Cut it out," the narrator says "I always liked that joke ." The narrator is played by Bob Saget, who stars alongside Coulier as best friends on Full House (1987), where Coulier used that catchphrase frequently.
The progression from Robin Sparkles to Robin Daggers is very similar to the real life career of Alanis Morissette who, before releasing Jagged Little Pill, had come out with a couple of light pop albums in Canada and went simply by "Alanis". Robin Dagger's vocal style is also reminiscent of Alanis.
Jeanatte (Abby Elliott) who played Ted's girlfriend from Season 8 is in real life, Chris Elliott's daughter. Chris plays Mickey Aldrin, Lily's father in the series.
In the "P.S. I Love You" video, Robin makes reference to God being a she. This is another reference to Alanis Morrisette who played God in Kevin Smith's "Dogma". In Kevin Smith's Askewniverse movies, God is always referenced as a she.