Disney Jr is not available in HD yet on Comcast
They do have a HD channel, but it is for all the Disney channels. it is called Disney XD.
Disney is channel 25 and nick is 24
879
Channel 879 on HD
259
807
894
It is 188, I'm not sure for HD
Comcast in Nashville, Tennessee broadcasts the SEC Channel on 718 SD and 1738 HD.
55 if you have comcast
Nickelodeon, which is 679 (HD) 40 (non-HD)