The problem with this episode is that it moved away from the fantastic observational, character comedy that the show was know for and instead we get slapstick and cheap gags. The originals happened mostly in real time, in one setting and with no music soundtrack other than what the characters were watching on tv. Here we have a new, unfamiliar setting, new characters added and an episode which takes place over a longer time period; including comedy montages and music to show the passage of the day. The original show broke ground by leaving behind all the traditions of sitcom, and instead just having realistic characters sitting in one room, with no studio audience, doing nothing and chatting. It was brave, and it worked amazingly well. So much so that other sitcoms of the time (Victoria Woods Dinnerladies for example) looked old fashioned and stagey next to this. But, in this special episode they have lost a lot of what made the show great, and now we have ridiculous slap stick comedy routines involving frozen turkeys and reclining chairs that makes it feel more like an episode of Last of the Summer Wine.
Having said that, it is still worth a watch. The cast are great, and there are some very funny moments. It's just quite different from the original 3 series.