Surprise announcement... and it technically has less to do with the 20th Anniversary, but with Kyoryuger VS. Go-Busters! May seem out of place, but it's an announcement which kinda-sorta ties into Abaranger's 20th Anniversary Celebration.

Ito did actually reprise her role of AbareYellow alongside her Red and Blue cast-mates. She just declined accreditation and had personal reasons for not appearing in person.

http://ukiyaseed.weebly.com/ukiyasee...-vs-go-busters

Fujiwara who most likely reprised his role as Dan from Zyuranger had somewhat of a similar situation. In his case, I believe it's because he was still working as one of the managers for SMAP at the time before they broke up and Johnny's supposedly has weird strict policies about their employees and entertainers making public appearances so he was uncredited as well.