Improvisational jokes presented in the bloopers. Some may not be improv, there is no way for me to tell.
If you like this check out the Always Sunny sketch show I compiled with all their dvd bonus gags:
Ep 1: https://m.youtube.com/watch?v=TbPXhq0Cw6o
Ep 2: https://m.youtube.com/watch?v=j7Llg2DGO2E&t=6s
Ep 3: https://m.youtube.com/watch?v=WgSzjkX75Og&t=790s