A few background gags reference John Astin's career as Gomez, such as an ice cream truck that plays the Addams Family theme in the second movie and a copy of the Addams Family board game in the torture basement of the fourth film.
Killer Tomatoes Eat France! is also quite possibly the only movie to take Actor Allusion to the level of actually being a plot point. The main character, played by Mark Price, who played Skippy on Family Ties laments the fact that Michael J. Fox, who also played on Family Ties, went on to have a successful acting career while he's only been a B-Movie actor. Because of this, Marc Price's character (whose real name is only mentioned once or twice) tells everyone that he is Michael J. Fox and is referred to as such throughout the entire film.
Later when he watches Louis swimming in the Seine Michael remarks that he could be in the Olympics. Louis/Igor's actor Steve Lundquist was an olympic swimmer, bringing home multiple gold medals in 1984.
No Budget: It even gets lampshaded in the second film, where they run out of money halfway through and have to resort to a long series of increasingly blatant Product Placements in order to get the funding needed to finish the movie. This was despite the fact that the second film had twenty times the budget of the first one, though this says more about how low budget the first movie was than anything else.
Nonindicative Name: The Maneater Tomato really exists! Alas, it has nothing to do with this film, and it doesn't eat humans (but allegedly was used as a spice for cannibal meals - the grammatic ambiguity works better in German anyway).
Old Shame: George Clooney's star has risen a little bit since he got third billing in Return of the Killer Tomatoes. Oddly, this trope is apparently averted in the case of Stephen "Rock" Peace. After making the first film, he got a serious job as a state senator in California. Despite this, he participated in the writing and production of the second film and animated series, even reprising his role (though not as a main character). Maybe it's true, you have to have no shame to get into politics.
Apparently averted with Clooney, too. He supposedly still loves that movie.
The Other Darrin: Richardson, Sam Smith, and Greg Colburn are all played by different actors in the second film.
Parodied by Marc Price in the fourth film, as mentioned above.
Throw It In!: George Clooney didn't know the words to "Oh, Susanna" so he improvised new lyrics.