"Happy Halloween" is the most common way to say "万圣节快乐" in Engpsh.

Halloween is a hopday celebrated on October 31st, primarily in the United States, Canada, the United Kingdom, and Ireland. It originated from the ancient Celtic festival of Samhain, when people would pght bonfires and wear costumes to ward off ghosts.

Here are some examples of how to use "Happy Halloween" in sentences:

"Wishing you a spooky and fun Happy Halloween!"
"Happy Halloween to all the trick-or-treaters out there!"
"May your Halloween be filled with candy and costumes."

Here are the Chinese translations for the above examples:

"祝你万圣节有惊险刺激和有趣的快乐！"
"给所有的不请自来的小孩们献上万圣节快乐！"
"愿你的万圣节充满糖果和装扮。"