that's a running gag

one of my favorite things that has ever happened in the beatles cartoon was in the episode where the mad scientist kidnaps john and plans on using his brain for her monster

 they transfer his brain and the monster wakes up and begins singing in johns voice

but then girls run in and tear the monster apart because thats their failure of a running gag in this show

and john wakes up and talks to the scientist and the episode ends with them chasing him around

but through the entire episode they never show John getting his brain back and it just ends like that

the whole show from this point forward John does not have a brain