When you "love challenge"!
One of my many favorite moments in TFTM 1986 was when Optimus just casually just orders the Dinobots to "destroy Devastator!". I mean reasonably speaking, they are close to the best option that isn't another combiner. Optimus's phrasing was very much in character for how to command the Dinobots. Make it simple to understand or they will probably just do whatever. But, out of context it sounds kinda funny for Optimus to be like "Hey, go kill that guy for me. I got other stuff to do!" and Grimlock be like "Don't threaten me with a good time!" (Loosely he said something like this as he was commanded and gleefully accepted, etc).
I can think of many more but do any of you have specific quotes that you like from the movie that are more hilarious out of context but make perfect sense in the movie's lore/story?