Those who have studied poetry know that rhyming is only one style of writing a poem. The real criterion that defines a poem is whether I am writing something that could not be conveyed in prose. The strict grammatical rules that define prose have no place for a real poem's sentiment. At the same time a poem doesn't need to convey a profound message in order to qualify. A poem that is cute may very easily fit the this criterion as well.
Humorous poetry has been written for thousands of years. Many of us do not know that the nursery rhymes that we sang as kids were made up to convey information of a delicate political nature encoded in what sounds like a silly children's song. Living in the western world, we are lucky enough to be able (in some cases) to freely speak our minds. However, we cannot take for granted the medium of humor as a way to convey information that may be politically dangerous.
There is a line from a country song that goes, "sometimes life's greatest gifts are unanswered prayers". It describes a man who sees his high school sweetheart at a high school reunion. He realizes how wrong they would have been for each other and how blessed he is to have the partner that he has. Many of us have similar stories. Many times we are lucky enough to end up not with the person that we thought was our soul mate but the person who is really meant for us.
The short poem is more challenging to write than a longer poem. It seeks to make every word count and mean exactly what is intended. A short poem has the added benefit of getting the message of poem through to the reader in a succinct way. There are many traditional styles of humorous short poems. The challenge is in getting your words into the proper number of syllables in each stanza. These poems have a technical element to them that contrast with the free flowing poems that are more common today.