Not that I was a huge fan of Kaufman (was always more a Chevy Chase / Steve Martin type of guy) but everyone needs to think about the time everything took place, it was a different world. While working on the Man on the Moon film I caught Jerry Lawler tearing up more than a few times, a great guy as well. Jim Carrey indeed was in character from the moment he sat in the make up chair till after he was done for the day. Friends and family of Andy's were on set seemingly daily and they all said it was as if time went backwards and Andy was there.
For the funeral scene some of the actors from Taxi and Lawler were legitimately sad. Jeff Conaway in particular expressed some regrets as did a few others as they didnt "get it" while Andy was alive. Jeff broke down and left set for a good period of time. While outside of the funeral set which was at a real cemetery I was talking to Milos Forman and even he legitimately questioned if Andy was actually alive or not. There was a scene filmed at the funeral if memory serves where someone walks in through the entrance and everyone turns to look just after the song. It was an improvised scene nobody was in on or knew about minus the camera operators and director. I forget if it was Tony Cliffton walking in but I also dont recall Jim Carrey being on set for those scenes so dont believe it was "Andy" walking in.
Talking with the Taxi cast at the funeral some were not there for the actual real funeral as they really believed he was pranking people not to mention there was still bad blood involved. But, those that were at the actual funeral including Bob Zmuda and family members know Andy is indeed gone as they had seen and identified his body. The fact people still talk about it and carry on with the joke keep it alive. Just as Elvis is alive playing cards with Jim Morrison and Abe Vigoda at Venice Beach, Andy's the one dealing cards.