"If The Emperor Had A Text-to-Speech Device", a show where the immortal Emperor after millennia finally gets a device installed that enables him to speak again, of which he immediately proceeds use to take out his 10.000 years of frustration and anger.
It starts as a couple of episodes of the Emperor learning what has happened to his Imperium during his absence but then spins out into this quite massive and entertaining plot, based a lot on what material was available at the time of the (very) stagnant WH40K universe (before the whole 8th Edition plot advance occurred). It is a quite hilarious take on an absurd universe with many jokes around how absolutely hilarious many aspects of it is.
Here is a remake of the first episode, the first couple of episodes are kinda low quality compared to now so the first was remade to give a better sense of current quality, recommend giving that a watch: