I am not writing to teach you how to tie a digital balloon animal in AutoCAD (which is possible), but rather create Bill of Material Callout balloons more effectively in AutoCAD.
In AutoCAD 2008 and 2010 there were many enhancements made to Multileaders “Mleaders” including making them a single smart object instead of a series of polylines and lines. Now you can tag items in your drawing with Mtext (the default), a block, or nothing at all. You change settings in the Multileader style access in the ribbon or Commandline at MLEADERSTYLE.
So lets take an example of using Mleader balloons, again not balloon animals but material callouts for your drawings.
You can launch the Mleader style dialog by selecting the lower corner arrow in the Leaders tab on the Annotate ribbon as use the command MLEADERSTYLE on the Commandline.
In the Multileader Style Manager select the New style option.
Next we will name this new Mleaderstyle based on the existing Standard style and name it as "Balloon”, and then select continue.
Now lets navigate to the Content tab and change the Type from the default Mtext to Block then select Circle as the source block. Note you can add your own types of blocks such as custom section callouts etc. Make sure you have your size/scale proper in the leader style or set it afterwards at the Commandline option MLEADERSCALE. You could have made it Annotative and automatically scaling based on view scales, but we are not going down that rabbit hole today.
Now lets place our new callout balloon. We select the Multileader command from the ribbon or use Mleader from the Commandline and the place the leader to an object such as I am on the pressure vessel tank saddle and then prompted for <TAGLNUMBER> at the Commandline and I use 1 as this is the first material I am tagging in this drawing. I could use A, B, C etc as well.
You can tag each item individually or even add multiple leaders from a balloon callout.
You can also collect a series of balloons as one using the icon or MLEADERCOLLECT. You select a series of Mleaders and it combines them into one string for the assembly. I call this the “Take me to your Leader” option.
Now I could create a Bill of Materials “BOM” showing what each callout item is with sizes quantity and perhaps cost. In AutoCAD Mechanical the BOM is all automatic. The callouts could also be a simple assembly sequence list.