Chartreuse with Yellow Kitten is a fanmade sing a ma jig duet. The big one has the same ears as the mermaid, has black circle eyes, an orange nose, and a dark blue mouth and also has the same hands and feet from the dark blue duet. The big one also has the same voice as the Lawn Green Sing-a-ma-jig. The little one is the same as the little one from the light blue fanmade duet, but is yellow with triangle eyes, red hair, has a nose and mouth color swapped from the little one of the dark blue duet. The little one has the has a voice mix of the Pink Sing-a-ma-jig and the little one from the purple duet, while singing, harmonizing and chattering in the same voice as the Orange Sing-a-ma-jig (while harmonizing the same way as the big one from the Plum duet). They sing "London Bridge is Falling Down."
They sign on, enter song mode, and sign off as follows:
Sign on: Big One: Hi!. Little One: Hello!
Entering song mode: Big one: Song! Little one: Sing it!
Sign off: Big One: Bye Bye! Little One: See You Later!