Reducing the size of Lazarus's compiled executables is fairly frequently commented on in the Lazarus forum. The default is for the exe to have all of the debugging tags kept in so this makes for a bulky exe even though the app in itself may be modest .
I have modified a small app by Marien van Westen from 2006 to enable you to compress your app to a very reasonable size.
Example: The compressor can work on another instance of itself to reduce its size from 19.5MB to 1MB.
I am packaging it so that versions exist for both Windows and Linux. There will be packages with just the necessary executables for both and a source package.
These will be uploaded soon onto my website and I will post in the Lazarus forums that they are available.