[While Sheldon is listening to a tape, Penny comes from behind and touches his shoulder, which scares him.]
Penny: Sorry, Sheldon. Do you have a second?
Sheldon: A second what? Pair of underwear?
Season 2
Penny: Sorry, Sheldon. Do you have a second?
Sheldon: A second what? Pair of underwear?
Season 2
[While Sheldon is listening to a tape, Penny comes from behind and touches his shoulder, which scares him.]
Penny : Sorry, Sheldon. Do you have a second?
Sheldon : A second what ? Pair of underwear?
Season 2
http://www.tv-quotes.com/shows/the-big-bang-theory/quote_20841.html