Heart Candy

The comment on Heart Candy can have one of eight different flavor phrases: 
 * "All yours."
 * "Be mine!"
 * "Hot lips."
 * "I LOVE YOU"
 * "I'll follow you all around Azeroth."
 * "I'm all yours!"
 * "You're mine!"
 * "You're the best!"

Source
Heart Candy can be found inside a. Each time the bag is used, one of the eight Heart Candy items is created. In addition to the saying, it also says , the character who opened the Bag of Candies creating the item.

Achievements
The World Event achievement for the Love is in the Air event requires you to eat all eight of these items. The odds are good that it will take more than one Bag of Candies to complete the achievement. This is in turn part of the Fool For Love meta-achievement.

As these candy hearts can be traded and auctioned off, it is not truly necessary to open bags of candies to complete this achievement.

Probability
The odds of creating any one of the eight on any use of the bag appears to be equal, one in eight of any of them, and after considerable digging, one comment on WoWHead (for the spell, Create Heart Candy, #26678) backs this up, but there does not seem to be a reliable source to verify this with.

Figuring out how long it takes (how many bags, 10 sample each) is intractable if you view it as a and attempt to follow each branching probability tree. However, the achievement can be viewed as a series of eight s; each characterized by a between outcomes "new candy" and "no new candy". Each binomial distribution has an expected time to success of 1/p, p being 8/8, 7/8, 6/8, 5/8, 4/8, 3/8, 2/8, and 1/8, and the expected times are additive, 8/8 + 8/7 + 8/6 + 8/5 + 8/4 + 8/3 + 8/2 + 8/1. The results is that it on the average takes just over two bags (about 21¾ samples) to complete this achievement.

This can be misleading; there is no cap on how long this can take; the distribution of samples to complete is weighted toward the low end with a shrinking number requiring more and more samples. Think of a long crane arm with a heavy counterweight. The bulk of the people attempting this achievement will complete it with only two bags and a few people will take much longer.