How do I make an upside down question mark in Google slides?

One way is to do it via insert symbol but possibly the quickest is press and hold the alt key and type in 0191.

OR

In Microsoft Word 2007:

Go to the Insert tab

Click symbols and then "More symbols..."

Find the exclamation mark

You should see an option called "Shortcut Key...". Click it

Under "New shortcut key..." press "Alt" and then press "1"

Next time you need an upside down exclamation mark press "Alt" and "1"

Your done!