When does a practical joke go to far?

I was reading another blog tonight, one that I recently found and really like. Funny guy. He was talking about some pranks he'd pulled years before. It made me think..... Is it possible to go to far with a prank?

Mr X and I are always joking around. I love messing with his head and he's a good sport about it. I've had our daughter help me out a few times. So far our favorite was last year. It took a bit of time, but the payoff was well worth it.
While he was at work, I pulled out all of his underwear and carefully sewed the seams together. Then I folded them back up and put them away.
I'm a light sleeper so I always wake up when he gets up for work. I'll never forget his reaction when, at 4:30 that morning, he tried to pull out a pair. He kept pulling until they were all out. Then he picked up one and started shaking it wildly. I pretended to be asleep as he shook it and mumbled. He finally got one of them seperate. Or so he thought. I lost it when he put them on and started to walk to the kitchen for his coffee; a trail of underwear following behind him.
He did get me back. We had a lone rat in our garage. Naturally, it was enough to ensure that I wouldn't be going anywhere near the garage while he dealt with the thing. 20 minutes later he came running in with a bloody finger. When I asked what happened, he told me that rat bit him and then got away. As I'm picturing rabies shots and wondering if it'd be possible to find the rodent, he was almost giddy watching me panic.
That one might have been almost too far, but here we take what every opportunity to poke fun at each other.