First make sure you’re collaboratively editing the same document.
Preferably on different positions in a very long (and unbelievably ugly coded) file.
Let the fun begin:
- Open up a multi line comment and never close it.
- Repeatedly press Cmd+A to highlight _everything_ so the screen for all the others starts to flash in your editing color
- Simply paste in A LOT of blank lines so the functions, the others are currently working on, scroll out of their view
- Sneak in some nasty syntax errors and wait for someone to save the file to test their newest edits
Some more ideas?