When you hear Chinese people say, "Don’t be a 电灯泡 (diàn dēng pào)！" Your first reaction may be—“Wait, what? What do you mean by ‘don’t be a bulb’? Of course I am not a BULB!” However, you will realize that this bulb is not the real bulb; actually it refers to the third wheel.
Why does 电灯泡 mean the third wheel? Many people think that it is because the bulb is always too bright for the couple to maintain their romantic atmosphere. Nevertheless, the original and accurate explanation of 电灯泡 is from Cantonese. As a popular Cantonese saying goes, “电灯胆（泡），唔（不）通气”. It can be roughly translated as "the bulb is not ventilated (because of its vacuum inside)".
The Chinese word for “not ventilated” （不通气）can also describe people who are unschooled in the way of dealing with other people. Therefore, the derivative meaning of 电灯泡in this situation is the third wheel, someone who doesn’t know how to behave properly when dealing with couples.
wǒ bù xǐ huān hé wǒ de qíng lǚ péng yǒu chū qù wán 。zuò diàn dēng pào zuì tǎo yàn le ！
I do not like going out with my couple friends. Being the third wheel sucks!
dàn shì lǎo bà lǎo mā làng màn shǐ lǐ de Ted yǐ jīng zuò le bā nián de diàn dēng pào le ！tā hǎo xiàng cóng bú jiè yì 。
But Ted from the TV show How I Met Your Mother has been a third wheel for 8 years. He doesn't seem to mind at all!
hēi ，xiǎo nà ，xiǎng hé wǒ qù kàn diàn yǐng ma ？
Hey Xiao Na，do you wanna go to the movies with me?
hǎo ā ！wǒ yuàn yì ！jù shuō fù chóu zhě lián méng fēi cháng
Yes! I would love to! I heard The Avengers is really.........
hái yǒu wǒ nán péng yǒu ？
......and my boyfriend?
wǒ jù jué dāng diàn dēng pào ！
I refuse to be the third wheel!
语言点 Language Points:
介意 jiè yì
E.g. 你介意我开窗户吗？Do you mind my opening the window?
我不介意加班。I don’t mind working overtime.
愿意 yuàn yì
willing to; would like to
E.g. 你愿意当志愿者吗？ Are you willing to be a volunteer?
Would you like to come with me or would you prefer to stay here?
据说 jù shuō
it is said that; they say
It is said that French people are among the most romantic in the world.
It is said that if you make a wish when you see a meteor, your wish will come true.
They say another school will be built here.
拒绝 jù jué
to refuse; to reject, to turn down
E.g. 我拒绝了她的好意。I rejected her kindness.
她拒绝了他的求婚。She turned down his proposal.
你的拒绝让我感到十分为难。Your refusal puts me in an awkward situation.