Venny: You really like me?
Bonnie: Of course... you'll be my bunny buddy forever.
Bonnie the Bunny wants to capitalize the fact that Venny secretly loves him, despite him being an animatronic. Now he has Ven is his grasp, so he suits him up to make him his best friend, and perhaps, more than friend...
Here's a fun little fact: I love bunnies, and Bonnie from the Five Nights games had a strong influence on me of having my fursona as a bunny.
It also felt really weird to me not having the ears inside the empty mask. So despite it not being accurate, it just makes me feel better about it
Also, PURPLE OVERLOAD!!! (I may have forgotten the pink in Venny's ears... Just consider it him losing the color from Bonnie's hypnosis)