England and Russia are both part of the Allies and often interact with each other. In Episode 13, England wants to summon a devil with his magic to take an inhuman revenge on Germany. After conjuring it for the 2nd time (America interrupts him in the 1st), he is shocked when he has summoned Russia instead. Russia peeks his head from the pentagram and asks sweetly, "You called?". A frightened England tries to shove Russia's head back into the pentagram afterwords. When the Axis and Allies are both stuck on an island (which happens to be Seychelles), England brings his famed and cursed Busby Chair that has put more than dozens to their deathbed. As if mocking him, Russia sits on it and shatters it to pieces, leaving a panicking England flailing in horror.
This pairing is believed to be a love/hate relation, often gory. Fans think the pairing was created when England "accidentally" summoned Russia, instead of the Devil.
It could also be seen as England still trying to get some sort of revenge on America, following the saying of "the enemy of my enemy is my friend." Other speculations include that England might be trying to fulfill his "maternal" insticts by caring for the more childish Russia.
Sometimes, they are seen just bonding over the fact that they both were once huge empires that held great power in the world that are now not as powerful.