What have you done lately that would make us wonder if you've been nipping the cooking sherry again?

This is a very good question. I thought you were going to post in the main room. You should have. 

I'm not sure there a steadfast rule on its use (Nevan, you're never around when we need you), but I'll venture a guess, if it's fine with you. 

Either of the four examples you've posted are 100% grammatically correct in the use of the word "that" or lack of use. Inclusion of the word is more important in written form than in everyday speech, because a lot of what we say aloud is looser than what we write when writing that exact same thing.   I often catch myself inserting the word "that" after I've proofread something I've written, without it, it has that "it needs something" quality to it. I believe that the rapid nature of the spoken word when compared to the careful retrospect that is sometimes offered in writing makes a big difference here too. Use of the word helps clarify or specify points. 

It appears to all come down to personal preference. 

(This entire answer is my opinion; I did not research any source or style guide to check first. I stand behind my response with utter confidence.)



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And I have utter confidence in your response.  :-)

That "it needs something" quality resonates and is usually how I feel when adding "that." The sentence just reads better with it. 

I thank you for helping me solve my long standing grammar mystery! Guess sometimes it's good to have an expert in the house.  :-)

(long-standing)

 I couldn't resist. 

I'll keep the angry villagers away..... this time.  ;-)

Yes, we're quite accustomed to seeing you like that, but where are your panties this time?


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Obviously, since you noticed them missing, you must have taken advantage of me while I was passed out.  


Thank you! ;-D

Have you noticed, Randy? She's thanking you for it. 

I'm torn between accepting thanks for a job well done, or being a good little Boy Scout who wouldn't have perpetrated such a dastardly deed on an unknowing victim. 



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