The Judoon leader is named "Pol-Kon-Don". This is a tribute to BBC online producer Paul Condon, who died in 2019 and was a huge fan of Doctor Who.
The Doctor's line "A platoon of Judoon. Near the moon." mirrors a similar line spoken by the Tenth Doctor in Smith and Jones (2007) ("Judoon platoon upon the moon...").
As The Doctor is talking to Ruth in the cathedral after the Judoon fight, there is a rainbow pattern that appears behind The Doctor from sunlight through a cathedral window. Unlike her shirt, the colors are in the correct spectral order (red, orange, green, blue, violet).