Sheldon does not have a cousin Leo.
The Big Bang Theory Season 1, Episode 10
Leo, this is Penny,
our friend and neighbor.
The Big Bang Theory Season 1, Episode 10
Of course not, there's no cousin Leo,
there's no intervention.
The Big Bang Theory Season 1, Episode 10
Whom most people call Leo,
but he also answers to Lee.
The Big Bang Theory Season 1, Episode 10
...emotionally wrung out from the work
of convincing Leo to go back into rehab.
The Big Bang Theory Season 1, Episode 10