Premiere: Underdog
- Review, by Glenn Kenny: "...a longer version of the film could conceivably have held children rapt…longer. But that same film would probably have sent adults screaming for the exits, subsequently leaving the children in need of adoption." [Rat
- http://www.premiere.com/moviereviews/3997/underdog.html

New York Daily News
- Review, by Jack Mathews: "Made for viewers old enough to appreciate a talking pooch but too young to read or write about it." [Rating: 2.5 out of 4]
- http://www.nydailynews.com/entertainment/movies/2007/08/04/2007-08-04_have_no_fear_caped_k9_movie_isnt_a_dog.html

Wikipedia
- Article describing plot, cast, and merchandise.
- http://en.wikipedia.org/wiki/Underdog_(film)

MovieWeb: Underdog (2007)
- Facts and figures, synopsis, videos, photos, and news.
- http://www.movieweb.com/movies/film/41/3941/summary.php

Yahoo! Movies: Underdog (2007)
- Details, trailers, cast and credits, reviews, photos, links, and a message board.
- http://movies.yahoo.com/movie/1809426137/info

IGN Movies: Underdog
- Provides information, news, videos, and a photo gallery.
- http://movies.ign.com/objects/483/483091.html

IMDb: Underdog (2007)
- Photo gallery, plot outline, cast list, trivia, quotes, user reviews, and a message board.
- http://www.imdb.com/title/tt0467110/

Rotten Tomatoes: Underdog
- Review links, synopsis, critical consensus, credits, photos, trailers, news, box office numbers, and a forum.
- http://www.rottentomatoes.com/m/underdog/