I hated it, even though I love Prisma Illya. Here's my history with the series:
2006 = I have absolutely no idea that the first of many "Fate/stay night" anime series starts airing. This is a grimdark (sometimes to a silly degree) supernatural deathmatch franchise. It stars lots of revived fictional or historical heroes.
2011 = a pisstake gag anime comes out called Carnival Phantasm, which I haven't watched yet.
2013 = I have absolutely no idea that the first of many "Fate/kaleid liner Prisma Illya" starts airing. This is a magical girl pisstake of "Fate/stay night", with its seasons being 1, 2wei!, 2wei Herz!, 3rei! and one day hopefully a 3rei Herz!.
2015 = I jump in cold and watch 2wei! ep.1, with no context. (I'd never seen any Type/anything shows, be they "Prisma Illya" or otherwise.) It seems okay, but I decide against continuing with it.
2016 = On a whim, I give "Fate/kaleid liner Prisma Illya" another go. I love it and become a massive fanboy. I blast through everything in a few weeks.
2017 = a movie comes out (Oath Under Snow).
2018 = I watch the 2017 movie and sort of approximately like it, but it's almost entirely "Fate/stay night" with very little "Prisma Illya".
2019 = a pisstake gag OVA comes out called "Fate/kaleid liner Prisma Illya: Prisma Phantasm". This may or may not be connected with Carnival Phantasm. I watch it and... well, here we are.
Now, let's get something straight. This OVA is full of references to and characters from the Prisma Illya universe. Clearly I'd need to refresh my memory to get all the jokes... but (a) I have a feeling that some of them might come from other "Fate/whatever" franchise branches, and (b) why should I of all people need a refresher? I love the show. I've watched it all. I've even read some of the manga. If that level of familiarity isn't enough for someone to watch this OVA, then something's wrong. I'll keep my copy of this OVA for the day when I rewatch it all from the beginning, but I'm not holding my breath.
3rei! ended in September 2016 on a cliffhanger. Since then, all we've had is one loosely related movie and this OVA.
We meet a twenty-something ramen owner with an old man's voice. His ramen is so spicy that his customers faint and faceplant into their bowls. He doesn't try to hide these (possibly dead or drowning) victims, yet more people keep coming in.
There's a TV chat show with a sister and her brother, who's a monster. This monster becomes the OVA's main character, e.g. being forced to work as a maid by girls with halberds. The Kaleidosticks look for replacement magical girls and make inappropriate choices. People play a game of hide-and-seek.
It's... no. Just no. I hit the fast-forward button after twenty minutes. I didn't care. It's just random garbage. Presumably it's supposed to be funny, but that's an informed guess rather than, say, having even considered laughing at any of it. (It's somewhere between "unfunny" and "unable to tell if that was meant to be humour".)
This is Part One of my review of this OVA. Part Two will follow in some number of years, after I've done that mega-rewatch. Maybe I'll like it better then?