Strange mess of a film; enjoyable overall, but could have been excellent
Just watched this again after not having seen it since 1981 (well, or given the release date, I probably saw it in early 1982). The beginning--the air traffic controller stuff, Max Fielder's (Chevy's character) Murphy's Law series of problems, etc., is friggin hilarious, with tons of rapid-fire, layered jokes, many relatively subtle or conceptual.
However, once Max gets home after being "slimed" by the nuclear waste, the tone and unfortunately the pacing completely change. To me it plays like they were making it up as they went along from that point, and they didn't really know what to do with the material. There are still enough great moments, but they never capitalize very well on Max's new abilities, and there are way too many "dead spots" where they're kind of just treading water. Also, too much of Chevy's performance in the second half of the film consists of doing relatively inscrutable mugging.
The fact that they eventually decided to do a demonic possession spoof was fun, although it doesn't make a whole lot of sense in context, and it's ultimately undercooked as a possession spoof and a bit too serious.