In Measure 42 (Pg. 13), Mama bear sings "Mamas in the mud, mamas in distress". This a musical reference to the song "Roses Turn" from the Musical Gypsy. Below is a Musical theatre Masterpiece performance of Broadway and Movie Actress Bette Midler performing the 11 O'Clock Number "Roses Turn". 

At the end of this number, Lord Farquad sings a "And no one's gonna bring me down" and does a high riff. This is in reference to the Act 1 finale number of the musical Wicked. In this number the Wicked Witch of the West, Elphaba (Idina Menzel who you know as the voice of Elsa from Frozen) makes the choice to stand up to the Wizard and fight for what she believes is right in standing up against the Wizard. Glinda, the good witch of the north decides to stay complacent and tries to convince Elphaba not to use her voice even though she knows that the Wizard is doing wrong. At the end of this number Elphaba takes flight in the final notes of defying gravity. The end of this number is known as a symbol for using your voice and for conintuing to fight for what you beleive is right. 

At the end of "Forever", Dragon sings "You're gonna love me" in a riff. This is a direct reference to the show stopping number "And I am Telling You I'm Not Going" from the broadway show DreamGirls. The number below is Jennifer Holliday, the original Effie. Ms. Holliday is a Tony award winning actress. Her performance of this number received a standing ovation every night and world wide fame.  (Fun Fact: this is Mr. Pele's favourite Broadway performance of all time and reminds him of why he loves musical theatre. The raw talent and emotion of this performance gives him chills and tears every single time) 

Not so much a reference as it is a song from the actual movie. Written by Niel Diamond in 1966, this song was first recorded by the Monkees. In 2001 this song was covered by the band Smash Mouth for the movie Shrek. This song once again hit the top charts. Watch silliness and fun from the movie! The Song "I'm a Believer" has become a theme song for the Shrek series as it was once again covered by the band Weezer at the end of the final installment Shrek Forever After.