Shrek's Father is a character in the Shrek series.
Shrek the Third
In Shrek the Third he is mentioned during the fire scene, and it's revealed that he was a cannibal ogre who tries eat his son, Shrek by bathing him in BBQ sauce and he put him in sleep with an apple in his mouth.
Shrek the Musical
In Shrek the musical he appears at the Start singing Big Bright Beautiful World.