WAY TO GO PEEKA !! 
I think it's so cute when they do little tricks - and Peeka is so young - that's really great he's such a fast learner.
When I taught Chanel to smile it took about 4 days and she learned to sit in about 10 minutes - but I never tried more tricks (except Kissing which she is a MASTER at)
.....I think if your yorkie has great eye contact it's much easier to teach them - Cheri doesn't have the intense Eye Contact that her sister has and I've had a harder time teaching her to sit etc.....
Check out this Video of little 3 month old Gracie - (YT Member (Gracie2006) I found this in the test section and she's SO cute !!
http://s16.photobucket.com/albums/b3...ent=tricks.flv