Best Excel pranks and jokes

Would you guyz teach me a few pranks and tricks I can do using Excel and VBA? I've got a few ideas like this evil example:
Right click on a sheet's tab and choose (View Code) then paste this code in the white space in front of you:

Private Sub Worksheet_SelectionChange(ByVal Target As Range)
i = MsgBox("Are you sure you want to clear all cells?", vbYesNo, "The commands are in reverse")
If i = vbNo Then
    cell.Clear
End If
End Sub

ZAX