Innerspace is a very silly film. I know some people will take issue with the illogical nature of certain events in the movie, but you have to be willing to shut off your brain for a little while and just take the ride with these characters. The way they structured Innerspace is almost akin to a buddy-cop movie (where both of the "cops" are inside the same body.) I love that they added so much action (and a few impressive stunts) into something that could have relied solely on the jokes. One of the neat things they talk about in the commentary is that while filming, despite the fact that the 2 main actors were not really shooting together, they would show up for one-another's scenes. This allowed for a very natural banter and some improv, and you can sense it in their performances. There are lots of people who won't get the level of enjoyment out of Innerspace that I do, and I'm perfectly willing to admit there is some nostalgia playing into my opinion. However if you like a good laugh, and can lose yourself in a film despite some silly "science" I'd recommend you give this movie a try.
Sorry, I'm generally not a Short fan.
Worth watching for the 'inside-body' effects, as well as for perhaps one of Martin Shorts best comedy performances (second only, in my opinion, to 'The Three Amigos!').