"Can I put clothes on my Chihuahua?"
The answer to the question varies as much as Chihuahuas themselves do. Chihuahuas, as with most other dogs, really don't need to wear clothes most of the time. There are some breeds, such as the hairless Chinese Crested, that do well with clothing due to lack of their own "clothing". And, many Chihuahuas do well with clothing too, especially in particularly cold times or places, as Chihuahuas are very much "warm weather" dogs. They really don't care for the cold, and so many welcome a warming sweater or jacket when the temps plummet.
But then, there are some that.....well, let's just say...don't so much welcome it. There are a variety of ways that your Chi may tell you that he does not, indeed, like the extra layers that you have added to his body. He may run around the house like a mad dog, bumping into walls and furniture, screeching and howling the entire way, until either you catch him, or he finally manages to get most of the offensive material off and dragging behind him.
Or, he may stand stone still, too afraid or too uncomfortable to move, glaring at you or looking unbelievably pitiful,and stay that way until you pity him enough to take the horrible mess off of him. And then, there are those that will calmly, rationally, RIP the offensive garment off of themselves and hide it under a cushion or bed to ensure, at least in their minds, that you will never find it again, and therefore, certainly could not ever attempt to cover them with it again.
Remember though, while these antics of the tortured Chihuahua may be amusing, your Chi is trying to tell you something. I think that if he could actually tell you what he's thinking, it may sound something like this "Please, beloved human, do not put an extra cover on me again, because I do not need it and I do not like it. If you insist on covering my beautiful fur with those horrid garments again, I will be forced to hate you forever."
Seriously though, whether or not you can dress your Chihuahua depends entirely upon the Chihuahua. If your Chi needs clothing for any reason, because he is cold or anything else, he will gladly and happily wear the clothing that you put on him as long as it does not hurt or bother him with rubbing, choking or constricting his movement. If he is not wearing the clothing....if he insists that it must come off....please take it off. Don't assume that he'll get used to it. Some may get used to it, though they will likely never enjoy wearing it, but many never get used to it and it's not only a bother to them, but an expense to you to keep replacing what they destroy trying to get it off. In addition, unhappy dogs can hurt themselves trying to get out of the offending clothing, and that is definitely not going to make you happy either.
*A side note....please be careful what clothing you choose to put on your Chihuahua. You'll want to be sure that you do not put too much pressure on the neck and trachea. Also, you won't want to constrict the movement of his legs, and I think it's also a good idea not to put anything on him that will bend his ears down, as this can damage the cartiledge and his ability to stand his ears up as they should be. Basically, the clothing that you choose should allow your Chi to move and act the way he normally does or it is not appropriate for him.*