The English names and texts for the new Hallo and Ween monsters have been revealed in a video from the official Twitter account:

Hallo, the Spirit of Tricks
DARK/Fiend
Level 4
0/0
If this card is Normal or Special Summoned: You can activate this effect; if you still control this face-up card, your opponent chooses 1 of these effects for you to apply.
-This card gains 800 ATK for each Fiend monster currently in your GY.
-Inflict 500 damage to your opponent for each Fiend monster in your GY.
If this card is destroyed by battle or card effect: You can send 1 monster your opponent controls to the GY.
You can only use each effect of “Hallo, the Spirit of Tricks” once per turn.

Ween, the Spirit of Treats
LIGHT/Zombie
Level 4
0/0
If this card is Normal or Special Summoned: You can activate this effect; if you still control this face-up card, your opponent chooses 1 of these effects for you to apply.
-This card gains 800 ATK for each Zombie monster currently in your GY.
-Inflict 500 damage to your opponent for each Zombie monster in your GY.
If this card is destroyed by battle or card effect: You can Special Summon 1 monster from your opponent’s GY to your field..
You can only use each effect of “Ween, the Spirit of Treats” once per turn.