I'm searching for some cute first underpants for a 2 yr old.

How exciting to shop for first time underpants. I suggest finding a pack that comes with at least 6-7 pairs, that way you have enough for emergencies..just in case your little one has an unexpected accident.
From amazon I found a pack of 7 pairs for a little girl in princess theme. Every little girl would like to be a princess, what better way to encourage her than with princess underpants.
From e-bay, I found a 3 pack themed of the DC superheroes for a little boy. My little boy thinks he is a ninja turtle and when he wear his ninja turtle underwear he thinks he can do all sorts of flips and fight crime haha. It is too cute.
From http://www.gap.com I found a 7 pack for everyday of the week, each pair has cute designs. Gap may be a little more expensive, but reviews show that it is a better buy because their quality is soo much better than most other brands.
Goodluck with your purchase and congrats on the newly potty trained little one!

The Childrens Place has alot of choices on cute underwear for boys and girls!  They have a 7 day panty pack selling for $16.50

• Made of super-soft cotton
• Pre-washed to reduce shrinkage so a great fit is guaranteed every time
• All are fashioned with an elastic waist for all-day ease
• An artfully designed tagless label provides itchless comfort
• Scalloped trim at elasticized leg openings adds girlish charm
• Packaged in an adorable plastic case complete with zipper closure and carrying handles
• In a seven-pack, with assorted designs and screen prints
• Imported

They have a boys 3 pack of briefs selling for $7.50

• In comfy combed cotton
• Pre-washed for softness and reduced shrinkage
• Elasticized waist for all-day comfort features a PLACE logo print
• A tagless label provides itchless comfort
• Rib-knit trim for a shape-keeping fit
• Pack of three: one solid and two printed with rockin' designs
• Imported