Similar to Rule 34, Rule 34.2 is an addition to the 100 rules of the internet that defines a common stereotype that did not exist in the original founding of those rules. In this case, Rule 34.2 is used to describe the existence of a pony variation of literally anything using the obscure art-style of the infamous show; MLP:FIM. It's entire existence is supported and expanded by bronies.
If the phrase "Joe mama" is used to someone who you are married to, you have to buy them 7 onigiris.
<someone's spouse>"Joe mama"
<that someone's spouse>"where is my onigiri's?!"
<someone's spouse>"what why?"
<that someone's spouse>"IT states it in rule 3425!"