For me:
*Keiron Self (Roger) in My Family.
*Ivan Kaye (Bryan) in The Green Green Grass.
*Russ Abbot (Hobbo) in Summer Wine.
And others but aren't coming to me at mo. 
Bad actors that ruin shows
The guy who played the verger in Dad's Army surely tops (or bottoms) all these?
Pretty much any supporting actor in Some Mothers Do 'Ave 'Em...
"Mr Spencer!!!" *shakes fists*
A general level of over-acting in comedy which has yet to be surpassed.
Mr Peacock's boss in Are You Being Served?.
Can't remember his name.
Massive Ears. No talent.
Edward Sinclair was the Verger, Nicholas Smith was Mr Rumbold.
Neither are as bad as Roger Lloyd-Pack in Dibley or The Old Guys, or Dr Who, or whatever he is in. OK as Trigger, not OK as anything else.
Quote: Jon Rob @ June 15 2009, 2:47 PM BSTThe guy who played the verger in Dad's Army surely tops (or bottoms) all these?
Check out War Dance ! !
Rumbold weren't that bad, not was The Old Guys.
I found that there were a lot of 'extras' with a few lines in The Mighty Boosh that were pretty bad and disrupted the comedy especially in this past season.
The Horrors spring instantly to mind. Hey, look kids, we've got the Horrors. They can't act for shit, but we've got them.
Mina Anwar in the Thin Blue Line, who also played a mother in the Sarah Jane Adventures, replacing the equally bad Juliet Cowan (who was also in Pulling).
Quote: Lazzard @ June 15 2009, 6:08 PM BSTMr Peacock's boss in Are You Being Served?.
Can't remember his name.
Massive Ears. No talent.
Haddaway an ...!
Mr Peacock???? Captain Peacock, thank you!
Mr Rumbold (first name Cuthbert, very apt) was brilliant! Perfect example of an incompetent manager. Plus Nicholas Smith played piano and accordian for the musical numbers, and his jug-ears were the subject of several fine jokes.
Quote: Tim Walker @ June 15 2009, 2:58 PM BSTA general level of over-acting in comedy which has yet to be surpassed.
For over-acting in comedy I do not think anything can quite compare with Never the Twain.
Yes, true, that was terrible. Someone seemed to forget to tell Sinden & Davies that they weren't on stage, there were in fact TV cameras and microphones within feet of them.
As an undemanding 10-year-old, I loved Never The Twain.
We were only really talking about the style of acting...