The main reason the Lego thing happened:
Lawyers are ridiculous when it comes to issues of intellectual property. Employees within the company probably appreciate the work, and the company itself probably appreciate it. It's a matter of marketing not wanting to be assosciated with NG, with the concept that legos are "kid friendly" and thus not appropriate for use here, and issues about having the logo. While others may have done this as a prank/spoof, odds are this came from Lego's lawyers (Disney and other large corporations can be the same way).
This is because current copyright/patent laws are overly protectionistic and because large companies can easily put financial pressure on individuals with the threat of lawsuit to cow them into giving up their rights to freedom of expression. Half of the film and its contents should be covered under fair use and laws related to freedom of expression. Unfortunately because of laws re: patents/copyrights being written as they are, companies are allowed to take this kind of action and do so regularly.
Charles Schulz's lawyers (acting without his knowledge) had a farm owner in NY (I think) had the farmer remove a painting he'd done of snoopy on his barn, because it violated Schulz's intellectual property rights. The farmer was NOT making money off of it, nor was it causing any financial harm to Mr Schultz. But lawyers will be lawyers, if they smell an opprotunity to profit from exploiting the letter (Rather Than the Spirit) of the law they will.
It's been my experience that many companies appreciate the fans and thus are hesitant to discourage them, but the lawyers are insistent that there remains a risk that their product could be lost if they don't act to protect their copyright.
In part as current copyright/patent laws stand we will be having things like Disney rereleasing its classics every 2 - 3 years for the next X hundred years. Patent/Copyright laws were NEVER intended to extend as long as they have been (will be) and they are being intentionally extended through the creation of "new content" featuring the original copyrights BEYOND their intended life expectancy in ways the lawmakers never intended.
This trend is a growing threat to NON corporate freedom of expression and individual right to hold copyrights as a whole. It should've been addressed in the Digital Millenium Copyright Act. Instead the DMCA has further eroded individual rights to free speech and enshrined abusive copyright practices into law. Existing Copyright and Patent law no longer offers equal protection to individuals as it does to corporations and franchises and represents a threat to our general rights and freedoms in the long term.
As Newgrounds grows, expect to see/face more of these idiotic/repressive attempts to control freedom of speech.
I strongly recommend any of you upset by this Lego issue to write your congressman/senator or equivalent protesting the unfair representation existing copyright laws offer to non-corporate entites/individuals. The rising costs of registering copyrightst and patents threatens to take the ability to create new ideas/technologies or creative works Away from individuals and destroy the fundamentals of the American Dream.
Unless we take action now to prevent the further erosion of individual rights when it comes to creating content/patents we may lose the right/ability to do so entirely within the next 100-200 years. Corporations and certain lawyers who support these ideas are working hard to take these rights away from the average everyday person (in many insidious ways). The death of freedom of expression is coming and may pass without any of us realizing its happened - if we do nothing. Along with that we'll lose the freedom and rights associated with being able to think for ourselves and we'll become nothing more than complete consumer wh**es enslaved to corporations that have more power than our governments do. Watch your respective governments closely as they may seek to distract the general populace as a whole (or even decieve them into believing what's being done is just, right and moral) while they push through that kind of legislation.