Did you know that the people in Ferelden celebrates April 1st,too? It is called Satinalia.
(according to a post from Bioware's Victor Wacter). In honour of this Bioware has released a DLC that contains 1) Prank Gifts or 2) Gift Packs. You can also buy a combo with both of those. There's a hand puppet you can give to Alistair and watch him do a puppet show.
Here's a snip from Victor's post:
(source:
http://social.bioware.com/forum/1/topic/94/index/2017890/1)
Satinalia, a day of wild celebration and sumptuous holiday feasts celebrated across Thedas, has arrived! In Ferelden tradition, gifts and pranks are exchanged on Feastday among friends, family and lovers. Now you'll be able to join the festivities and surprise your companions with gifts that may touch their hearts or offend their sensibilities.
Feastday gifts and pranks offer the player a chance to explore the approval system in Dragon Age: Origins at greater depth by making your companions despise or adore you. These packs are available for purchase individually or as a combo back containing both the Gifts and Pranks.
Personally, I can't wait to see what kind of puppet show, Alistair would stage...