Timeline:
4/20/2014: application sent out!
4/28/2014: Fingerprint fee is accepted
5/20/2014: Papa's fingerprints taken
5/29/2014: called USCIS, was told Mama's appointment letter lost, can go to do the fingerprint at any time, no appointment was needed!
6/10/2014: Mama's fingerprints taken
8/4/2014: no need for interview mail
4/8/2015 welcome letter received, card will be received in 3 weeks!
4/20/2014: application sent out!
4/28/2014: Fingerprint fee is accepted
5/20/2014: Papa's fingerprints taken
5/29/2014: called USCIS, was told Mama's appointment letter lost, can go to do the fingerprint at any time, no appointment was needed!
6/10/2014: Mama's fingerprints taken
8/4/2014: no need for interview mail
4/8/2015 welcome letter received, card will be received in 3 weeks!