- You may be looking for the in-universe series.
The Avengers was a television series which ran from 1961 to 1969. Sydney Newman, the creator of the series, later went on to create Doctor Who.
There have been several crossovers with Doctor Who and The Avengers:
- Party Animals: Emma Peel and John Steed attend Bonjaxx's birthday party
- The Dying Days: Emma Knight attends a party
- The Face of the Enemy: Little Storping (from "Murdersville") is mentioned
- Verdigris: Jo Grant reminisces about her friend Tara, implied to be Tara King
- The Sleuth Slayers: Georgie Price Jones (from "The Girl from AUNTIE") works with a man implied to be John Steed
- Riviera Shakedown: John Steed sees off Iris Wildthyme and Panda when they take a plane
- In the Sixties: The newborn Paul Magrs dreamt Emma Peel, John Steed, and Cathy Gale attended a party hosted by Dr Oho
- Hospitality: The Lesbian Avengers were likely named in homage to the series
Additionally, the DVD documentary Girls! Girls! Girls! - The 1960s (included on the 2008 release of The Rescue/The Romans) indicates that the character of Sara Kingdom was inspired by the Avengers character Catherine Gale, as played by Honor Blackman. Blackman would later appear in Doctor Who.
Other cast members who worked on both The Avengers and Doctor Who or its spin-offs include: Tom Adams, Anthony Ainley, Lewis Alexander, Terence Alexander, Ronald Allen, Dave Anderson, Keith Anderson, Paul Anil, Philip Anthony, Bernard Archard, Laurence Archer, Graham Armitage, Graham Ashley, Richard Atherton, Brian Badcoe, John Bailey, John Baker, Ken Barker, Peter Barkworth, Bernard Barnsley, David Baron, Patrick Barr, John Barrard, Reginald Barratt, Ray Barrett, Michael Barrington, Keith Barron, Timothy Bateson, Geoffrey Bayldon, Johnson Bayly, Kenneth Benda, Christopher Benjamin, John Bennett, Steven Berkoff, Michael Bilton, Honor Blackman, Isla Blair, Brian Blessed, Paul Blomley, Philip Bond, Peter Bowles, Peter Brace, Edward Brayshaw, James Bree, Ray Brooks, Maurice Browning, Hugh Burden, Jonathan Burn, Edward Burnham, Edward Caddick, John Carson, Heron Carvic, John Cater, Tony Caunter, Dallas Cavell, Robert Cawdron, Derek Chafer, Rosemary Chalmers, Dennis Chinnery, Alan Chuntz, Dennis Cleary, John Cleese, Noel Coleman, Sylvia Coleridge, Christopher Coll, Geoffrey Colville, Les Conrad, George A. Cooper, Kenneth Cope, James Copeland, Peter Copley, Billy Cornelius, Nicholas Courtney, Arthur Cox, Clifford Cox, Bernard Cribbins, Gerald Cross, Ian Cunningham, Alan Curtis, Peter Cushing, Iain Cuthbertson, Griffith Davies, Pamela Ann Davy, Billy Dean, John Dearth, Aimée Delamain, Roger Delgado, Edward Dentith, Roy Denton, Peter Diamond, Vernon Dobtcheff, Eric Dodson, Angela Douglas, Donald Douglas, John Doye, Paul Duval, Valentine Dyall, Hamilton Dyce, Leon Eagles, Clifford Earl, Donald Eccles, Mark Eden, Dennis Edwards, Clifford Elkin, Eric Elliot, Michael Elwyn, Tenniel Evans, Rio Fanning, Royston Farrell, Max Faulkner, Lee Fenton, Fred Ferris, Harry Fielder, Edwin Finn, John Flint, Eric Flynn, Dudley Foster, Eden Fox, John Franklyn-Robbins, Bill Fraser, Ronald Fraser, Leslie French, Martin Friend, Tex Fuller, Jimmy Gardner, David Garth, Frank Gatliff, William Gaunt, Donald Gee, Alan Gerrard, John Gill, Julian Glover, Michael Goldie, Maurice Good, Bill Gosling, Michael Gough, David Graham, John Greenwood, Ron Gregory, Joe Greig, David Grey, Paul Grist, Fred Haggerty, Neil Hallett, Peter Halliday, Roger Hammond, Janet Hargreaves, Michael Hawkins, Alan Haywood, Mark Heath, Arthur Hewlett, Donald Hewlett, John Hollis, Julian Holloway, Bernard Horsfall, Arthur Howell, Peter Howell, Stephen Hubay, Derek Hunt, Richard Hurndall, Barrie Ingham, Harold Innocent, Frederick Jaeger, Godfrey James, Robert James, Colin Jeavons, Peter Jeffrey, Reginald Jessup, Stratford Johns, Alf Joint, Hayden Jones, Norman Jones, Bernard Kay, Edward Kelsey, Eric Kent, Leonard Kingston, Gertan Klauber, Kristopher Kum, Burt Kwouk, Simon Lack, Alan Lake, Tony Lambden, Nigel Lambert, Duncan Lamont, Dinsdale Landen, Anthony Lang, Robert Lankesheer, Philip Latham, John Laurimore, Arnold Lee, John Lee, Penelope Lee, Richard Leech, Ronald Leigh-Hunt, Tutte Lemkow, Aileen Lewis, Rhoda Lewis, George Little, Philip Locke, Terence Lodge, William Lucas, Martin Lyder, Michael Lynch, Fulton Mackay, Victor Maddern, Philip Madoc, Kevork Malikyan, Ronald Mansell, William Marlowe, Marina Martin, Alan Mason, James Maxwell, Jack May, Ronald Mayer, Neil McCarthy, T. P. McKenna, Michael McStay, Murray Melvin, Ralph Michael, Martin Miller, Frank Mills, John Moore, André Morell, Charles Morgan, Donald Morley, Steve Morley, Wolfe Morris, Hugh Morton, Bryan Mosley, Declan Mulholland, Brian Murphy, June Murphy, Valentino Musetti, David Nettheim, John Nettleton, Derek Newark, Patrick Newell, Kate O'Mara, Tina Packer, Louise Pajo, Geoffrey Palmer, George Pastell, Michael Peake, Jacqueline Pearce, Morris Perry, Jon Pertwee, Paul Phillips, Robin Phillips, Donald Pickering, Leslie Pitt, Steve Plytas, Christine Pollon, Dinny Powell, George Pravda, Reg Pritchard, Roy Purcell, Keith Pyott, Godfrey Quigley, David Quilter, Rex Rashley, Mike Reid, Peter Reynolds, Aubrey Richards, Bill Richards, Edwin Richfield, Graham Rigby, Diana Rigg, John Ringham, Christopher Robbie, Michael Robbins, Ilona Rodgers, Anthony Rogers, Jon Rollason, Alec Ross, George Roubicek, Reed De Rouen, Peter Roy, Robert Russell, Peter Sallis, Ivor Salter, Terry Sartain, John Savident, Katherine Schofield, John Scott, Steven Scott, Tony Selby, George Selway, Maurice Selwyn, William Shearer, Douglas Sheldon, Barbara Shelley, Robert Sidaway, Jack Silk, Campbell Singer, Patsy Smart, Nicholas Smith, Edward de Souza, Henry Stamper, Valerie Stanton, Peter Stephens, Michael Stevens, Roy Stewart, Nigel Stock, Kevin Stoney, John Stratton, Malcolm Taylor, Rocky Taylor, Gareth Thomas, Peter Thomas, Talfryn Thomas, Eric Thompson, Royston Tickner, John Timberlake, Anne Tirard, Raf De La Torre, Harry Towb, Frederick Treves, Michael Turner, Jim Tyson, Edward Underdown, Brian Vaughan, Wanda Ventham, Hein Viljoen, Charles Wade, Gary Watson, Moray Watson, David Webb, Robin Wentworth, Alan Wheatley, Lionel Wheeler, Jack Le White, Reg Whitehead, Paul Whitsun-Jones, William Wilde, Jerome Willis, Sonnie Willis, Anneke Wills, Barry Wilsher, Neil Wilson, Frank Windsor, Francis De Wolff, Vincent Wong, Terence Woodfield, John Woodnutt, John Woodvine, Jack Woolgar, Peter Wyngarde and Jeremy Young.
Crew members who worked on both The Avengers and Doctor Who or its spin-offs include: Paul Bernard, Terrance Dicks, Gordon Flemyng, Ron Fry, Alun Hughes, Malcolm Hulke, Gordon Lang, Barry Letts, Peter Ling, Henry Lincoln, Bill Lodge, John Lucarotti, Terry Nation, Geoffrey Orme, Dennis Spooner, Robert Banks Stewart and Bill Strutton.