Birch, Please.

 Me: AAAUUGH! BWAHAHAAA!

John: What? [seeing cake] What IS that?

Me: [laughing]

John: Is it a cow? Buried face down?

Me: [still laughing]

John: Wait, no, I think it's a tree. A birch tree.

Me: [shrill cackling punctuated by honking, bugle-like snorts]

John: Is there a two-liter in that thing? Seriously, look; I think there's a soda bottle in there! Jen?

Me: [wiping eyes] Oh, so you're saying it's all bark and no bite?

John: Ug, that's terrible. We need some good puns.

Me: Hey, if you don't like my puns, you can make like a tree, and GET OUT OF HERE.

John: That's it. No more Back to the Future marathons for you.

Me: Awww. You are my density, baby.

Thanks to Amanda C. for proving there's nothing shady at all about a tree stump with two limbs.