Sheldon: We just leave the house on Friday night, and we return in the wee hours emotionally wrung out from the work of convincing Leo to go back into rehab.
Leonard: So he goes back into rehab?
Sheldon: Yes. But he can relapse if Penny ever invites us to go hear her sing again.
Leonard: You still told her I lied.
Sheldon: For a noble purpose, to spare me the social embarrassment of having a drug-addled first cousin, which I'm assuming is embarrassing, yes?
Leonard: I don't know. How am I supposed to remember all of this?
Sheldon: That's the best part. You don't have to. See, I told Penny that you would be embarrassed if you knew that she found out that you had lied. So she's agreed to operate as if the original lie was still in force.
Leonard: So she's expecting me to lie about going to a symposium in Pasadena, when in actuality we're pretending to go to a drug intervention in Long Beach?