Threat Quality Press has a great rundown of how to pull of a good midget joke, and why The Love Guru does not seem funny. In fact, the only time I considered grinning during the trailer was at a throw-away Don LaFontaine joke, and that has more to do with me sweating Don LaFontaine than any actual humorousness of the joke.
Midget jokes really aren't that hard, as TQP explains. Look, here's a decent one, and it doesn't even have midgets in it. Observe the pointed subversion of our expectations. Expectations, by the way, that are built on previous Mike Meyers midget jokes.
In un-related comedy news, check out the new webcomic Sigmund Freud vs The Male Nurse. Here's a page from yesterday's edition:
SFvtMN is by Mike Le, creator of Don't Forget to Validate your Parking, which in addition to being funny, also wins Le the title of "Only Comics Artist Who Creates Less Art Than Ryan North."