Both the opening and ending songs are amazing, with the ending song getting the most praise.
The overall musical score of the series is amazing also, since it shifts some tones of the series from being happy to more serious and grim subjects on some episodes. Ryosuke Nakanishi has a good talent of composing anime scores.
Base-Breaking Character: Mishil. In her debut episode alone she was considered a serious Manipulative Bitch which doubles as an Overt Operative in order to frame and blackmail other Cocotamas for her to take over the Cocotama House because she was lonely when she was born. Fans weren't happy on her characterization while some said that despite those flaws, she redeemed herself in the next episode and is now a part of the group.
Broken Base: The overall reveal that the series will replace Tamagotchi on television got some fans annoyed due to the series deserving a better sequel that GO-GO Tamagotchi!, while some said that the anime has been on life support and that Himitsu no Cocotama was a good successor to the previous series.
In Episode 1 Part B, Kokoro needs to build Luckytama a house in order to fulfill the contract, but when she is running out of time and it gets to be 12:00 AM is just too harsh. Though Luckytama thanked her for being caring to her and before he disappears he uses his magic one last time. This becomes a Moment Killer when they realized they have 15 minutes left and Kokoro successfully finished the house before midnight with Luckytama earning his first Happy Star.
Episode 6 got the Cocotamas lost in the forest while Kokoro and her class were grilling outdoors. Since they can't find their way back and their magic is ineffective in their own, Kokoro got worried and came looking for them. The Cocotamas didn't give up and decided to combine their magic in order to create a flying vehicle out of leaves to find Kokoro. After a while, they were tearfully reunited with her.
Episode 12 focuses on the Cocotamas alone as Luckytama was in charge while Kokoro's family is gone for three days. While decorating, there are conflicts between him and Oshaki about how they would decorate the Cocotama House for Christmas until she decides to leave permanently, with the others following though Melory is somewhat worried. After some fiascos and seeing that Luckytama is doing his best despite failing, the others return and reconcile with him while helping him finish decorating the house before Kokoro comes back.
Episode 17 had a rather heartwarming talk between Kokoro and her grandmother on the phone as she expresses about losing her friends that she keeps her secrets to (mostly the Cocotamas). Her advice is that Kokoro needs to be true to herself and her feelings.
Episode 39 features Kokoro and Nozomi going to an amusement park. While they are there they meet a young boy who is upset because his father had to work and wasn't able to go to the park with him. Ultimately they find out where the father is working and use Cocotama magic to get the father off work early so that he can spend time with his son.
Episode 62 had Nozomi attending a sleepover at Kokoro's house. Nozomi stated that she deeply misses her father and wants to go in his overseas expeditions with him, which he told her she would not be able to do until she grows up. She then reveales that her Cocotama contract wish is to grow up so she will finally be able to spend time with him. Meanwhile, Vivit has been going out on her own at night in secret looking for problems to solve so she can make Nozomi's wish come true much faster.
Narm: The love-heart pattern on Amanda's face makes her look charmingly cute, which somewhat diminishes any attempt she makes at being threatening, or really anything other than happy.
Tainted by the Preview: The reveal trailer of the series seriously turned people off due to them thinking that the series would be generic 5-minute-long anime... until the second trailer that aired in the final episode of Tamagotchi: Tamatomo Daishu Go! that confirmed it would be different.
Tough Act to Follow: In contrast to the Tamagotchi franchise and despite the good sales numbers, it's unsure if the series can get the same appeal as the former.