Bad Taste is a 1987 New Zealand science-fiction action comedy horror film directed, produced and filmed by Peter Jackson, who also starred in it and co-wrote the screenplay, along with Tony Hiles and Ken Hammon. Independently produced on a low budget, it is Jackson's first feature film. Jackson and friends take on most of the key roles, both on and off-screen. The plotline sees aliens invade the fictional New Zealand village of Kaihoro to harvest humans for their intergalactic fast food franchise, where they face off against a four-man paramilitary force.
https://en.wikipedia.org/wiki/Bad_Taste
It took four years to make and he got a noticeable bump in money near the end of production. That's why the aliens look like aliens at the end.
There is another big time gap in filming during a car chase scene. The car gains and losses a louver during the chase and the driver has put on a lot of muscle by the end.
I think the scene where he uses the chainsaw to enter the building is one of my favorites in any movie.