The Jargon File (version 4.4.7, 29 Dec 2003):

mickey mouse program
 n.

    North American equivalent of a noddy (that is, trivial) program. Doesn't
    necessarily have the belittling connotations of mainstream slang ?Oh,
    that's just mickey mouse stuff!?; sometimes trivial programs can be very
    useful.


The Free On-line Dictionary of Computing (30 December 2018):

mickey mouse program

    The North American equivalent of a "noddy program",
   i.e. trivial.  The term doesn't necessarily have the belittling
   connotations of mainstream slang "Oh, that's just mickey mouse
   stuff!"; sometimes trivial programs can be very useful.

   [Jargon File]

   (1995-04-10)