Uhm... not really. To back up a bit, MUCK characters (and other MU* or M* characters for that matter) usually have a specific species, gender, look, smell and way of speaking. (Yip, for instance, is a male chihuahua who "hablas" [Okay, so I didn't major in Spanish - sue me! <g>], and how he looks and smells can be seen on his description page). However, this is all just a bunch of data that can be changed at the user's (player's) whim - if i should get tired of playing a little dog I could easily (well at least compared to what I would have to do in the real world!) rewrite his data and turn him into a cat!
But what if I should change my mind later, or even decide to alternate between being a dog and a cat? Or maybe I would just like to switch back and forth between different descriptions of the same character? Sure, I could just keep copies of the different data sets on my own system and upload a different one every time I wanted a change, but that's a bit clumsy. Fortunately it does not have to be done this way, because someone thinking more or less as above once invented (?) the concept of morphing.
To put it simply, a MU* player can use a special program to store several sets of descriptions etc. and switch back and forth between them at will with just a simple order. If you look at their description pages, you will find that two of my characters use (or used) it in slightly different ways - Yip uses it to change his pose, Huwuda used it to change both his pose and his species!
[Okay, that's not really the whole truth - my "secret" character uses morphing as well, and for some pretty wild things too...! ;P]

So much for plain morphing, but what's a TRaM? That is an even wilder concept, and its full name is Temporary Random Morphing - TRaM! Or, in plain English (?), turning into a different form for a limited time period.
Okay, slightly plainer English then! At least it isn't Greek...
The concept usually takes the form of an object (which, like other MUCK objects, could be anything at all - a wishing well, a magic wand or a plastic surgery robot ;)) with an action connected to a program. When activated, the program will store your original data out of the way before overwriting them and starting a timer. When the timer runs out, your original data get restored and you are your old self again.
The probably most well known TRaM device on FurryMuck was the legendary (?) Vixen Vending Machine, which turned the user into a voluptuous vixen (!) for a while. (I understand it was popular with the foxes...) Others are more innocent and harmless (?).

Well that was the general explanation. The following pages contain some more info, ideas and reflections about both forms of shapechanging for the specially interested.