Kudryvaka was a stray mixed-breed dog found on the streets of Moscow. She was also the first living creature to be sent into orbit.
On November 3rd, 1957, the Soviets launched Sputnik 2, carrying Kudryvaka into space as a test. They had no plan for recovery of the dog, and so she also became the first living creature to die in orbit.
Though her name was Kudryvaka, or "little curly," she became widely known amongst Russians as Laika (a name attributed to several breeds similar to the Siberian Husky, which Kudryvaka was), and Muttnik amongst Americans as a pun on Sputnik. She was the first animal in orbit, but not the first one in space: the US and USSR had been strapping animals to the tops of rockets since 1947 in order to see the conditions of space on a living thing.
Though it was said after her death that she died peacefully and painlessly a week into orbit, medical sensors amongst other things show she actually died from overheating and stress just a few hours after the launch.
She is famed and beloved for her tragic story and also her importance in the research of space travel. Today stands a monument dedicated to Laika in Moscow, erected in April of 2008. The Space Race between the US and the USSR which proved as background to Laika's launch may be long over, but Laika's memory is not.
Graphic novels have been drawn (http://news.discovery.com/space/laike-the-russian-space-dog-finally-gets-a-happy-ending-110712.htm) and songs have been sung (http://www.youtube.com/watch?v=yZylEIgiOh4) and dubbed (http://www.youtube.com/watch?v=YvDx4Mg5YgM) all in dedication to Laika, who was 3 years old at the time of her launch and death.
Her face has additionally adorned a 1959 Romanian stamp, reading ""Laika, first traveller into Cosmos."
Sources: History 1900s.about, Space.com, BBC News, Wikipedia