This is another comic book written by Zack Whedon for Dark Horse comics featuring a character from Dr. Horrible's sing along blog. The comic partially explains part of Penny's personal life and gives some explanation as to why she is still single.
Dr. Horrible - Appears briefly getting beaten up in the park
Capt. Hammer - Appears In the same shot beating up Dr. Horrible
Wingspan - Appears fighting a giant robot
Wingspan vs Robot - On the first page in the background you can see Wingspan fighting the giant robot later mentioned
You literate little minx - On the side of Penny's cupboard there is a sticker that says "reading is sexy"
Control your animal - Probably noticed but outrageous dog walker manages to catch his hat as it flies off his head
Mysterious suited man - For no apparent reason a man in a suit walks half way up a path and then heads back down this is on the same page that Penny agrees to go out on a date
Hook line and Sinker - On the first page poking her head into a car is what you can only assume is a prostitute
Caring Hands - The name of the homeless shelter that Penny works at is called the Caring Hands Homeless Shelter and was possibly her inspiration for her song "Lend a Caring Hand".