John Steed visited Bonjaxx's birthday party at Maruthea. He participated in the bar fight started by a Meep. As the Seventh Doctor left Maruthea with Ace, he fought Captain Britain with Emma Peel. (COMIC: Party Animals)
Ace once told Gilgamesh that all good spies wore disguises, citing John Steed as an example. (PROSE: Timewyrm: Genesys)
In 1968, when Iris Wildthyme and Panda took a plane from Croydon Airport, John Steed saw them off. (PROSE: Riviera Shakedown)
When the Eleventh Doctor visited 1963 with Amy Pond, he mentioned John Steed as one of the people that made the 1960s "cool". (GAME: City of the Daleks)
When Fitz Kreiner wore a business suit with a briefcase and an umbrella, Samantha Jones thought that if he put on a bowler hat he'd look like John Steed. (PROSE: Revolution Man)
Behind the scenes
John Steed is the principal character of The Avengers. Julian Wadham plays him for Big Finish Productions.