A/N: I know this was explained in the Chicago version of the musical, but since the Broadway version left it open-ended (as far as I know), I felt the need to provide my own explanation. Because torturing Wednesday is just too much fun. ;)
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It was a lovely day in Central Park. The sun was shining, the bluebirds were singing, and the flowers were practically bursting with colorful blooms. Spring had come in all its full glory.

And so, dear reader, you can tell that things were bound to go wrong.

Lucas Beinecke certainly knew it. This was the kind of day when even going to the park was a vain endeavor- she never came out on sunny days. But the morning had been so perfectly overcast that he'd been willing to try.

And now the whole day stretched ahead of him, bright and beautiful and dull.

Just when he'd finally made up his mind to leave, though, a black-clad figure raced into the clearing and flung itself into his arms.

Maybe this day won't be so bad after all.

Before he knew it, his lips had found hers, and her nails were digging into his neck in that way that was pain and bliss at the same time, and he was reaching out to twine one black braid around his finger-

Or rather, trying to, because his hand met only the fabric of her dress.

"Wednesday?" he mumbled against her mouth. Getting the word out proved rather difficult- she seemed to be actively trying to silence him.

"What?" she replied between very enthusiastic kisses.

"What- mmf- what happened to your hair?"

"Bunsen burner accident." Conversation was clearly not on his beloved's agenda today. In fact, given the way she- Wow. That's new. For a moment, Lucas' mind was pulled irretrievably back to the situation at hand. But soon, curiosity again reared its head.

Oh, right. Answers.

With some difficulty, he broke away and held her at arm's length (trying to ignore her indignant glare). The braids were indeed missing; the ends of her hair now just brushed her collar, and it was parted on one side. The overall effect was far from unflattering, but something about her explanation didn't add up.

"Bunsen burner?" he said incredulously.

Wednesday rolled her eyes.

"Yes, Lucas. Surely you've heard of them." She attempted to return to his embrace, but he still held her off.

"Don't accidents with fire usually do more damage than that?"

Her expression would have made a wiser man stop talking and resume their earlier activities. But then again, a wiser man wouldn't have been dating Wednesday Addams.

"It looks great; I'm just wondering how you avoided getting hurt," he clarified.

The young woman, her glare now liable to make a tiger cringe, groaned and grabbed the front of his shirt.

"Listen. I leaned too far over the damn burner while doing an experiment and a spark caught one of my braids. I was able to put the fire out quickly, but I had to cut the other side so it matched. Got it?"

Without giving him time to respond, she pressed her mouth back to his. For a few minutes, the clearing was relatively silent. Then, another question occurred to him.

"But Wednesday, how did-"

"I don't want to talk about it. Shut up and kiss me," she growled, biting down on his lower lip and putting paid to further conversation.

It would only be four years later, around their second wedding anniversary, that she would inadvertently mention never having owned a Bunsen burner.