Kakashi and Iruka not getting along during their ANBU and Anbu prankster phases respectively is already an excellent concept in its own right. Still, I believe you can make it ten times funnier if Iruka befriends the "actually nice and not a killjoy" ANBU, Cat.
Iruka gets all three of them into the worst troubles possible. He's enjoying his time.
Personally, I think Iruka would befriend Cat when he's doing some work in the Hokage Tower- in the Hokage's office, to be specific.
And Cat is like "??? Why does the kid [he ignores that they both are in fact the same age] that glitter-bombed me last week have access to the Hokage's paperwork?"
(To be fair, that glitter-bomb was meant only for Hound; Cat just happened to be next to him)
Iruka picks up on Cat's curiosity and shows him in the- in Cat's own words "Konoha's Next Seals-master's way". He reorganized the Hokage Tower's entire archive system and changed or reinforced, in certain cases, their wards and barriers through seals of his own creation.
Yamato is AMAZED.
And to Hound's horror, next time he's patrolling in the village along Cat, Iruka Umino is about to prank him again but deflects his own harmless attack when his eyes drift to Tenzo's figure in surprise. Iruka even apologizes to Cat because "I was aiming for Hound and didn't noticed you were next to him- that was close" and Cat brushes it off, picking up Iruka's glitter bomb and walking towards him to HAND IT BACK, positing next to the prankster just to tell him:
"Here. I'm no longer near him".
Hound is too utterly dumbfounded and quite confused to process Iruka beaming at his cute kohai's words and proceeding to point it at his direction.
Bathed in pink glitter, Hound finds out these two have become friends.
