![Oh, this takes me back.
Leonard obsessing about Penny.
Oh, this takes me back.
Leonard obsessing about Penny.](data:image/png;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=)
Oh, this takes me BACK.
Leonard obsessing about Penny.
The Big Bang Theory Season 4, Episode 9
![Is Is](data:image/png;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=)
Is "BACK on track" a hint
that it has something to do with trains?
The Big Bang Theory Season 10, Episode 11
![So don't put that back in.
So don't put that back in.](data:image/png;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=)
So don't put that BACK in.
Breaking Bad Season 5, Episode 13
![No, I'm sorry. Wait. Please, come back.
No, I'm sorry. Wait. Please, come back.](data:image/png;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=)
No, I'm sorry. Wait. Please, come BACK.
The Big Bang Theory Season 2, Episode 18
![and take her back into Crown custody.
and take her back into Crown custody.](data:image/png;base64,R0lGODlhAQABAAD/ACwAAAAAAQABAAACADs=)
and take her BACK into Crown custody.
Game of Thrones Season 6, Episode 4