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Areas of this article contain spoilers about Double Back. Please proceed with caution.

Read at your own risk.

Double Back is the second of twelve special episodes of Numberblocks. This is the 122nd episode overall.


It's time for a time travel adventure! Sixty-Four's new time machine keeps sending the Numberblocks back in time. Can they double up in time to fix it?



  • This episode's description used to show that it's a crossover with Alphablocks, but it was later removed.
    • This tweet from the Numberblocks Twitter confirms that the crossover idea was either scrapped or was a mistake.
  • This episode was put on iPlayer on Friday, two days before it is aired on TV.
  • This episode's logo is a parody of the movie "Back to the Future".
    • Sixty-Four's time machine is a parody of the DeLorean car.
  • This episode has a time-travel plot, where a certain character travels back in time to change an event in the past.
    • The type of time-travel featured in the episode is a "time loop", where the main character gets sent back 2 minutes in the past, in an altered timeline, with the only difference being that the main Numberblock is twice their size. This repeats until Sixty-Four is the one heading to Sixty-Four's time machine, to plug the time regulator.
    • There are a total of six different timelines in the episode.
  • Sixty-Four is the biggest Numberblock in this episode, meaning she is the biggest to appear in the specials in total.
  • The episode uses dynamic physics in some parts such as when Ten and Three fall into the ball pit and some of the balls roll out.
  • Despite being a special, people still refer to it as the 122nd episode of Numberblocks.
  • Octonaughty's lair is seen in the background in some scenes.