Jedward

The Ninth Doctor used Jedward as an example of fleeting fame. (COMIC: Doctormania)

Clyde Langer mentioned Jedward whilst he was trying to entertain the baby Sky. (TV: Sky)

The Twelfth Doctor mentioned having once taken Jedward to Karfel. (AUDIO: Flight to Calandra)

Alternate timelines
In world that never was, (TV: The Wedding of River Song) @Jedward_The_Talented_Twin_Terpichores spoke to Charles Dickens on Prof. T. Witter's Instant Messaging Service. (PROSE: Just a Minute...)

Behind the scenes
Jedward were a 21st-century singing duo composed of brothers Jonathan and Edward Grimes.

In the parodic sketch One Born Every Minute, the Eleventh Doctor warned Dawn and an expectant father that their babies would grow up to be the most frightening creature imaginable — Jedward.