Collision Course (audio story)

 was the sixth and final story in the audio anthology The Legacy of Time, produced by Big Finish Productions. It was written by Guy Adams and featured Tom Baker as the Fourth Doctor, Louise Jameson as Leela and Lalla Ward as Romana.

Publisher's summary
Fallout from the temporal distortions has now reached Gallifrey. To find the cause, Leela and Romana remember travels with the Fourth Doctor to the same world, at different times. The enemy is revealed, and it may take more than one Doctor to prevent the destruction of everything!

Plot
Wibbly-wobbly, timey-wimey!

Cast

 * The Doctor - Tom Baker
 * Romana - Lalla Ward
 * Leela - Louise Jameson
 * Tompino - Alan Cox
 * Punshon - Richard Earl
 * Ankarrie / Sirens - Rebecca Kilgarriff
 * Bernice Summerfield - Lisa Bowerman
 * The Doctors - David Bradley, Frazer Hines, Tim Treloar, Peter Davison, Colin Baker, Sylvester McCoy, Paul McGann, David Tennant
 * Alien Voice - Nicholas Briggs

Uncredited

 * Pilot 4 - Jane Slavin

The Doctor

 * The Eighth Doctor and Tenth Doctor are both fond of hugging.
 * The Tenth Doctor calls the First Doctor a teenager, to which he objects.
 * The Sixth Doctor wants to give a speech before they dematerialise the prototype TARDIS, but the others don't let him.
 * Romana notes that the Doctor generally likes to "treat a TARDIS as if it's a theme park ride" while at the console.
 * The Seventh Doctor teases the Third Doctor for having "an excellent nose" for most things, referring to the size of it.
 * The Third Doctor was in the middle of tinkering with Bessie before joining in on this adventure.

TARDIS

 * The prototype TARDIS is not dimensionally transcendental.
 * The Tenth Doctor comes up with the term "guardfox waveforms" to make his contributions and that of the first two Doctors sound important. The First Doctor calls him on his bluff.
 * The Sixth Doctor has to adjust for temporal drift.
 * The Third Doctor hands off the helmic regulator to his fifth self.
 * The Doctors manage to increase power to the temporal buffers by extracting it from their own TARDIS, through remote power transfer. They need to do so to avoid a temporal shockwave.
 * The Eighth Doctor has to instruct his third self to look between the bakelite TV set and the Goblin Teasmade to find the power link-up in the Seventh and Eighth Doctor's control room. Though the Third Doctor does not hear, he finds it anyway.

Continuity

 * The Fourth Doctor notes to Leela his affection for ginger beer. (TV: The Android Invasion)
 * The TARDIS becomes a regular, empty police box as a result of a time paradox. (TV: Father's Day)
 * Romana tells Leela that TARDISes were originally built to have six pilots. (TV: Journey's End)
 * The Sixth Doctor mocks the Fifth Doctor for the amount of time it took him to get Tegan Jovanka to Heathrow Airport. (TV: Time-Flight) The Seventh Doctor does the same with the Third Doctor about his attempts to get to Metebelis III. (TV: The Green Death)
 * After witnessing the behaviour of his tenth incarnation, the First Doctor states that he's putting "serious consideration to never regenerating". He would later try to prevent the inevitable before regenerating. (TV: The Doctor Falls, Twice Upon A Time)
 * The Eighth Doctor complains about the Seventh Doctor's "midlife crisis", having "inherited a gothic castle" inside his TARDIS from him. The Seventh Doctor insists this redecoration was the result of mere "spring cleaning". (TV: Doctor Who, AUDIO: The Settling)
 * The Fifth Doctor encourages his other incarnations with the words "Brave heart... all of me". (TV: Earthshock, et al.)