Professor Brian Cox makes space for role in Postman Pat
The physicist, 49, appears in animated form, voicing the role of space expert Professor Farrow in an episode of the show which airs on Wednesday.
In real life, the pop star turned TV presenter is in Australia, filming Stargazing Live.
In the CBeebies show's Greendale setting, Professor Cox's alter-ego Professor Farrow recreates the surface of the moon.
The episode will see Postman Pat, who has always yearned to be an astronaut, attempting to make a special delivery of a space suit after his van breaks down.
:: The new episode airs at 7.25am on Wednesday.