The Sweden winger is impressing in his second season at the City Ground.
Harris, who left United earlier this year, told the Manchester Evening News: "Anthony sent me a lovely video and he said 'come to a game, I'd love to see you'. He got me tickets for Nottingham Forest's game against Liverpool at Anfield and I took my dad and son with me, which was really nice. Anthony came on and played really, really well.
"As soon as the game finished, and this shows you how quickly players go on their phones, I was leaving the ground and received a text from him asking whether I was still here.
"He'd been looking into the away end trying to find me. His mum turned up and I'd not seen her for 10 years, so we had a big hug and were talking about how he was always late.
"Anthony finally came out, he saw me and his mum together and he went 'oh no' because he knew he was going to get stick for taking his time! But he gave me a lovely big hug.
"The first thing he said to me pretty much was he should have scored. He said he should have chipped it and I said yep, but he knew anyway. He told me he thought about me in the away end when he missed that chance... I'm a coach from years ago and it gave me chills.
"When we signed Anthony, I got a phone call from Derek Langley to say we've got a boy here who has just landed in Hyde. I remember going to his first game and phoning him back after 25 minutes to say we need to sign him right now and that was the old-school recruitment.
"He came from Sweden with his mum, he didn't speak much English and was very quiet, but I used to sing a chant with his name and say they're going to sign that song for you one day.
"In the video he sent me, he said 'do you remember that chant you made for me? It made me feel brilliant'. Forest sing a song that is similar now and it's the little things like that."