Who is your favourite supporting character? By this I mean someone who isn't the focus of the episode (so Sally Sparrow is out) and appears in only one or two episodes (maximum) so Brigadier Lethbridge-Stewart is also out..

I'll go for Bannakaffalatta, who shows humour, pathos and bravery in his brief stint, with Isobel Watkins also in the running.

Lynda (with a Y) sticks out to me from Nu-Who, she picked things up very quickly and showed confidence (and seemed to fancy the Doctor a bit).

Kathy and Larry Nightingale in Blink

Nancy in the The Empty Child/The Doctor Dances

Anita in the Library two-parter

Lynda with a Y in the Series 1 finale

Jethro in Midnight

The Vinvocci couple in the End of Time

John Cleese's character (who appeared for about 30 seconds) in City of Death

Jazz musician Courtney Pine who played some exquisite Jazz in Silver Nemesis

The Beatles playing "Ticket To Ride" in The Chase

I'd also like to say the Tollkeeper (played by Ken Dodd) in Delta and the Bannermen, as I really like DatB and I greatly admire KD as a comedian. However, I cannot as the character was rubbish and Ken Dodd's acting was atrocious.

How many was Wilf in? he won't count will he? Dammit.

Too many to mention. Sally Sparrow, Nancy from The Empty Child, Lady Christina, Jago and Litefoot from The Talons of Weng Chiang, the wonderful Griffin the chef from The Enemy of the World, the two workshy guards in Warriors Gate...

Still, if pressed for an all time favourite, it'd have to be the permanently bewildered Griffiths, played by Brian Glover, in Attack of the Cybermen. An absolutely perfect performance.

Come to think of it, Nancy was very much a central character, so doesn't meet the OP's criteria, so I'll go for Doctor Constantine (played by Richard Wilson) instead.

Classic series - Richard Mace in The Visitation

New series - If Sally Sparrow is out, then Nancy in The Empty Child/The Doctor Dances

Kevin Stoney (Tobias Vaughn) - The Invasion

Graham Crowden (Soldeed ) - The Horns Of Nimon (Nahh only joking)

I was going to say Maxil (Colin Baker) in Arc of Infinity...

But actually, my favourite character out of all Who is probably Duggan in City of Death.

New Who. I liked Simon Pegg's character in the Jagorafess story. (Somebody can correct me on the character and story)...

Ahem....The Editor in The Long Game

Thanks. It's been a while since I've watched it.

Sister Lamont.
TERRIFYING.

For Nu-who, its got to be Clive (Mark Benton) from Rose , I love that character!

For Classic Who, without a doubt Nyder from GotD!
(Thank you, thats what I wanted to know!)

sereis 4 , the two sontaran episodes , unit officer ross poor bugger got kiled off tho!

Same here, really wish we'd seen him again

Are we allowed Harriet Jones - given that she has a supporting role in all the episodes she's been in, and there's only really been a few?

No? In that case, I'm taking Malcolm Taylor from Planet of the Dead.

Donna's grandad
Rose's mum Jackie
Harriet jones - Dying to know what happened to her after the part 1 series 4 finale.

Larry Nightingale.

What happened to her? I imagine her incinerated bits were given a decent funeral.

I'm going to say Harriet Jones, Charles Dickens, Jabe, Jackie Tyler and Adam from Series 1, how about Blon Slitheen from Boom Town as well?

Series 2 it has to be Jake and Sarah Jane, Jackie maybe also and also Yvonne Hartman.

Series 3 has to be Professor Yana and Chantho from Utopia, Timothy from the Family of Blood, Brannigan from New Earth.

Series 4 has to be Ross from The Sontaran Stratagem, Agatha Christie from The Unicorn and the Wasp, River Song from Silence in the Library, Jethro from Midnight, the Italian dude in Turn Left, Harriet Jones (again), Luke and K9 from The Stolen Earth, Adelaide from The Waters of Mars and Rassilon from The End of Time. I know, a lot, so I shall also narrow it down to my Top 5....

in no particular order

Harriet Jones
Agatha Christie
Jake
Jethro
Ross