First you should know "必胜客" (bì shèng kè) is the official Chinese name of Pizza Hut like 肯德基 (kěn dě jī) of KFC.
Then I guess you must know what does 剩男/剩女 mean. 剩 (shèng) means “remaining; left" in Chinese so 剩男/剩女 refers to those men/women who are over 25 years old but still single or unmarried.
Another new word for you: 剩客 (shèng kè). It is a general joint name of 剩男 and 剩女.
Clever Chinese netizens classified them into 4 groups.
25 years old to 27 years old ones are 初级剩客(chū jí shèng kè, junior single dogs). These people still have courage and are struggling to find their love so they are also called "剩斗士" (shèng dòu shì, original word "圣斗士" comes from a famous Japanese comic Saint Seiya. "斗士" literally means fighter).
28 to 31 years old ones are classified as 中级剩客(zhōng jí shèng kè, middle single dogs). These people are so busy in their job so they have no spare time to meet and date someone. They are also called "必剩客" (comes from 必剩客, literally means someone who must be remained).
32 to 36 years old ones are 高级剩客(gāo jí shèng kè, senior single dogs). They survived their cruel workplace but they are still single. They are called "斗战剩佛" (dòu zhàn shèng fó, original word "斗战胜佛" is the title of Sun Wukong, the Monkey King).
Those people who are over 36 years old are classified as 特级剩客(tè jí shèng kè, grand single dogs) and called "齐天大剩" (comes from 齐天大圣, another title of Sun Wukong. 齐天 literally means "equal as the sky") for no other special reason.
Now you must know the differences between 必剩客 and 剩女. Just like the differences between a chick and a hen.
How to use:
These words belong to Chinese network languages, can be used to refer to yourself or anyone else. Basically they are not offensive.
e.g. 我是个没人要的剩女，呜呜呜。(Wǒ shì gè méirényào de shèngnǚ, wūwūwū.)
他是一个黄金剩斗士。(Tā shì yí gè huángjīn shèngdòushì. "黄金剩斗士" refers to a rich one, especially a man.)
你现在还不打算找女朋友，将来是想做必剩客吗？(Nǐ xiànzài hái bù dǎsuàn zhǎo nǚpéngyǒu, jiānglái shì xiǎng zuò bìshèngkè ma?)