Ok let’s dispel this myth right now, it’s been stated in multiple panels that the actors and directors did that this isn’t remotely true. Neil Flynn himself has stated numerous times it isn’t true and that it’s a big disrespect to the writers that people keep saying this. He has done a lot of alternative dialogue on multiple takes which they use when editing and on occasion they would put in “janitor says something funny” but it wasn’t for everything and he didn’t just”say what he felt like”. How would that even work if a lot of what he says has to tie into the plot that’s written? People want to credit him for everything, when he’s a part of the team and a good bunch of writers came up with his character and his dialogue. If he said whatever he felt like then he would have ended up being fired, that’s not how making a tv series works. It’s a collaboration between all the actors, directors and writers.
Love hate and love to let a grudge build for years on years just planning fucked up things to do to them. Best is to tell them that you will kick their ass soon or do something horrible then forget it. The antsipation will keep building up as they think you are actually still going to get revenge. Soon it will drive them crazy as their own mind does all the work and you don't have to do a thing to get revenge other than watch. Never ever get revenge early it's like wine better when it ages.