Changes Through the Years ​​

Disney Dollars have changed quite a  bit since 1987,  But they have also kept some key features too.  Key features starting with the 1987 Disney Dollar that still continue through today:
Disney Dollar Tinkerbell logo
Tinkerbell has always graced the Disney Dollar being a key element since 1987.
On every bill Scrooge McDuck is the signing treasurer. [Scrooge McDuck Disney dollar Treasurer Signature] Scrooge is considered to be the business administrator, bank manager type, money saving, along with being cheap.
Scrooge McDuck's Signature
Disney Dollars just like other currency is not printed in unlimited quantities.  Each bill has a specific serial number series year.  These numbers/letters are specific and individual to each bill in order of when they are printed from 00000001 to 99999999.  However, each set of bills has a limited quantity some have small production run such as for the limited edition $50 or large quantities for the $1.
Example - Serial Numbers
On each side is a statement of denomination in the image below is the One Dollar  on the reverse of the bill the the we can see the printer words, on the Obverse, or front, is the Numeral form
Value in numeral form (bottom of bill)
Since 1987 we have always seen an "important" character on each bill.  These are Disney Characters of which primarily have been Mickey Mouse on the $1, Goofy on the $5 and Minnie Mouse on the $10. However In 2007, 2011, and 2014, a non character portrait has been used.
Disney Dollar Mickey Head Logo
On each bill is and insignia to the left of the Main Character on the observe of the bill.  This is typically the  head of Mickey Mouse with an offset printing of the letter "D" inset. This image has changed seven times since 1987. 
Happiest Celebration on Earth Logo
Celebrate Today! Logo
100 Years if Magic Logo
Mickey Mouse 1928-2008 Logo
2014 Mountain Series Logo
20 Years of Disney Dollars Logo
Pirates of the Caribbean Dollar Logo
2013 Villains and Heroes Logo