They're back together! All seems right in the world when Penny is dating Leonard, don't you agree?
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Amy lends her assistance to Sheldon in this scene. The guy needs help with a new project.
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The Big Bang Theory Season 5 Episode 14 Quotes

Penny: You mean like a beta test?
Leonard: Well, technically, this would be an alpha test. A beta test requires people that weren't involved in the development of the appli....
Penny: Seriously, do I not get credit for knowing beta test?
Leonard: No, absolutely you should.

Leonard: I missed you.
Penny: You see me all the time. You sure you don't just miss the sex?
Leonard: Well, yeah, the sex with you is pretty great. Have you ever tried it?
Penny: I have. You're not wrong.