After Vince is seen exiting the mirror world, he is seen exiting it again in one of the mirrors behind Mr. Susan.
Several times, you can see the flesh wrists of some of the Grim Reapers. Once when Phil is driving Vince to Monkey Hell and during the musical bit when the shot changes to the Reaper behind the desk
When Vince falls into the mirror at Naboo's place, as the mirror ripples you can see bits of bright blue, revealing that it was a blue-screen shot.