Mockbusters, as usual, are films made with plots or themes that are similar to the original, more popular film. Most mockbusters are made in an attempt to cash-in or capitalize on the popularity of certain films. I'm going to list some films that are kinda like mockbusters, and that some people might confuse these for the real movie.
#1: Aliens vs Avatars (Alien vs Predator and Avatar)
On September 20, 2011, Tom Cat Films and Sterling Entertainment unleashed Aliens vs Avatars. The film would count as a quasi-mockbuster because it looks like a crossover between Alien vs Predator and James Cameron's successful 2009 film Avatar. In the movie, a group of college students find themselves in an intergalactic war between shape-shifting aliens and a group of violent aliens. The film is probably a cult classic, and might appear on the possible television reboot of Mystery Science Theater 3000.
#2: The Black Bat Rises (The Dark Knight Rises)
In 2012, Canadian filmmaker Scott Patrick made The Black Bat Rises (original title: Rise of the Black Bat) in an attempt to cash-in on the widely-anticipated release of The Dark Knight Rises, the third and final film in the Christopher Nolan Batman trilogy of films. The mockbuster was distributed by Brett Kelly Entertainment and Dudez Productions. The titular hero in The Black Bat Rises is recruited by his grandfather to the Order of the Black Knights, a take on the League of Shadows, and becomes a crime-fighter under the name of the Black Bat. The main villain in the movie is named Simon Darth, possibly a Darth Vader rip-off, who heads an evil corporation that threatens to infect the whole world with a replica of the Black Plague. The Black Bat is also like a cross between Batman and Daredevil, and he also carries a gun, as the poster above indicates (Batman rarely uses guns in the comics). In a way, this would probably beat Yarasa Adam-Betmen (the Turkish Batman flick from 1973) by about 60%, considering the production values of both mockbusters. Some people who never read comics, as well as some confused old people, might accidentally buy this for their kids or so, thinking it was The Dark Knight Rises, but this might be a favorite amongst fans of mockbusters/B-movies.
#3: Kickassia! (a possible take on Kick-Ass)
In April 2010, Kick-Ass became one of the most popular adult superhero films (along with 2009's Watchmen) throughout the United States. A month after its release, however, Channel Awesome and the Nostalgia Critic gang (associated with Doug Walker and his That Guy With The Glasses website) unleashed a film that might be called a rip-off of Kick-Ass. However, some people might confuse this for Kick-Ass because of its title, but the film is not really a mockbuster per se. The film was a six-part web series that was turned into a feature-length film called Kickassia!, and it is about the Nostalgia Critic gang as they try to start a takeover/coup of the Republic of Molossia, an actual man-made country located on an acre of land on 22 Mary Lane, Dayton, Nevada. The costumes/weapons that the Nostalgia Critic guys use can be similar to Kick-Ass, and the guys' witty humor kinda shows that, too. Molossia's leader, President Kevin Baugh, also makes an appearance in the film as a comedic version of himself. The film was also a subject of the first episode of Emer "Hellsing920" Prevost's popular YouTube series Reaction & Review. The film also includes silly plot points such as the cult-like worship of a deity named "Santa Christ".
#4: Captain Battle: Legacy War (Captain America: The First Avenger)
So, Saint James Films had to strike while Captain America; The Winter Soldier was in production, eh? That's right! In 2013, the aforementioned studio, along with Sterling Entertainment and Tom Cat Films (the same two companies that made Aliens vs Avatars), unleashed a cash-in on the Marvel Cinematic Universe Captain America movies, known as Captain Battle: Legacy War. The film is centered around an American Gulf War fighter named Sam Battle who is injured during an attack, thus given the chance to be injected with a secret serum by his friend, a scientist named Brandon Storm. A Red Skull-esque villain, a clone of infamous Nazi soldier Heinrich Himmler, tries to take over the world, so Sam Battle goes under the alias Captain Battle, and tries to stop the Himmler clone's iron grip on the world. People, whether confused old guys or people who don't read comic books, might also confuse this for the Captain America movies.
#5: Pirates: Quest for Snake Island (the Pirates of the Caribbean franchise)
In 2009, two years after the release of Pirates of the Caribbean: At World's End, the third movie of Disney's famous film franchise, Canadian studio Dudez Productions, the same studio that unleashed The Black Bat Rises, released Pirates: The Quest for Snake Island. The plot is almost like that of Pirates of the Caribbean, except that it uses characters created by the producers of this movie, such as BlackJack Cutter, who was based off of Captain jack Sparrow. I don't know how else to describe this, though.
#6: Star Quest: The Odyssey (the 2009 Star Trek reboot)
In 2009, filmmaker and television producer J. J. Abrams released his reboot of the popular Star Trek franchise. That same year, however, Tom Cat Films and Infinite Spectrum Productions unleashed Star Quest: The Odyssey, rivaling on the popularity of the Star Trek film reboot. However, the film also borrows elements from Star Wars and Battlestar Galactica, so its simply a mish-mash of all those franchises, combined into one giant mockbuster.