The Rabbit?? It has BIG TEETH

How would you go about wild shaping into the rabbit from Monty Python and the Holy Grail. The one they have to use the holy hand grenade on?

Rules as Written answer: You can’t. There is no Beast statblock for it.

The Killer Rabbit is so powerful largely for comic effect, as MP&tHG is a farcical comedy movie, and despite what memes may say, D&D is a serious fantasy game (although of course many groups use it for comedic fantasy).

There are two stat blocks I can think of that might work for your purposes:

The first is the Hare from the Icewind Dale: Rime of the Frost Maiden book. It is just a plain snowshoe hair with no attacks.

The second is the Almiraj from the Tomb of Annhilation adventure. They are a one-horned rabbit (a bunicorn?) that attacks with the horn. You could reflavor the Horn attack into a bite.

or you just shapechange into a bear, use the bears stat block so all balanced rule wise and everyone is happy. But the description of the scene involves a very dangerous looking rabbit instead of a very dangerous looking bear ... like it wouldn't matter to me done that way.