Couple Bomb: Averted. The two leads were dating at the time (and have since married). The director wanted to cast a real-life couple because the chemistry between the two was so important. The film ended up making $4 million on a budget of under $500,000.
No Budget: Was made on $500,000 in spite of the massive, Hollywood-quality CGI monsters that play a small but vital role in the film. The locations, including monster-smashed landscapes and various exotic South American locales are also pretty impressive. The director, Gareth Edwards, made all the CGI on his home computer, most of the locations were stolen, and many supporting characters were simply bystanders recruited to improvise scenes on the spot. The boats and trucks in trees were probably left there by previous hurricanes.
Sleeper Hit: Made on a budget of $500,000 and made approximately eight times that at the box office.