* When they assist the exhausted Kelvin to his room near the end, his body blocks the light but occasionally his body moves so the light can come through and blind the camera. This parallels the discussion about destroying the visitors with a burst of light.
* Burton's extended unexplained car ride is (in my opinion) a nod to the 2001 star-gate. It's quite brilliant how Tarkovsky shows that what Kubrick achieves with exotic special effects can be achieved with everyday footage if we just look from the right angles and play the right soundtrack.
* In the old footage they watch near the start of the film, we see stylistic artwork of important figures in the background. These would certainly be informed by Tarkovsky's expertise on Orthodox Iconography (see his "Andrei Rublev").
* Interesting to compare and contrast the visitors with Kubrick's "HAL". The visitors are purely physical and totally unaware of where they are/what's going on. HAL is purely mental and totally omniscient. Both raise all kinds of interesting metaphysical questions about personality and the soul.
* The swirling water-plants at the beginning and end of the film are evoked by the paper strips the crew hang up on their ventilators.
* Near the beginning, Kelvin stands outside in pouring rain, as if not noticing it, when he could escape it by walking just a few feet. This becomes very meaningful with part of the twist in the ending.
* Young Burton talks about how gigantic the child he saw in Solaris's ocean was. Later, when the visitor is frozen from the dry-ice suicide attempt, we briefly catch a glimpse of her face reflected in a concave mirror which makes it seem monstrously gigantic.
Right now the entire film is available free on YouTube: https://www.youtube.com/watch?v=LutMHAeCfLU&t=5193s (turn on closed captions unless you speak Russian)