Since it’s “tzarich talmud”, I’ll explain.
(It’s almost like explaining a joke)
“Rosh Chodesh” means the first of the month (generally speaking Jewish ones). First of April is known as April First, fool day. Since it came on Yom Tov, we hadn’t an opportunity to observe it properly.
I suppose the character in the CR known as Popa (who is obviously adept at fooling people, pulling their bluff) has a field day, a “Chagiga” on that day.
This “shtikel” should be learned (and chazered) with an upside-down thumb motion, beard (if any) in the other hand (talmud-like)