Earlier in Origins, Sonic is briefly replaced by Batman who promptly reacts to a rampaging Monster Knuckles with "This is bad."
Shrek makes frequent cameos in scenes involving Knuckles. Said cameos make more sense when you remember that Knuckles here is basically Eddie Murphy (Hence Shrek calling Knuckles "DONKEY." That and Knuckles quickly shouting "Coming to America!" as he throws a zombie Cream off of him in Origins)