Contender for both the most brilliant and, paradoxically, most stupid species ever encountered!
It is understood (though heaven knows how these things get reported) that sometime shortly before their homeworld stopped existing, out of sheer boredom, its inhabitants finally "perfected" a means of escape and theoretical colonisation of other worlds and dimensions!
As you will know, it is much harder than mere fiction would have us believe to cross the barriers of dimmensional space and time, yet this is exactly what these clever little so-and-sos did!
Yes, indeed, they invented a functioning time machine, capable of transporting several hundred Addendumdums in a single instance!
However, the flaw in the plan came when they realised that despite being able to go wherever they pleased, with astonishing accuracy, they were limited timewise to anywhere between 2 and 4 seconds before the destination universe collapsed and all reality ceased... Unfortunate, to say the least. Moronic, to say the most.
This makes it very hard to get an accurate description of their appearance, demeanour or, indeed, anything else about them, as an average of 3 seconds is just too short a time to make notes - even my shorthand is not that good!
Right thing to say should you ever meet one: Goodbye.