I think you did an amazing job at this! I like the colours, shadows, and designs and the poses for both of the characters are awesome! XD Also I love how you did the text! I love how the classic version of sonic is on top of the modern version of sonic XD and how the classic version is holding the slice of cake. Also its very smart to have the background not complex to make it look nice and simple, if you did a complex background it woulnt have looked as nice as how you did it already
Overall, I think you did an outstanding job at this.
OMG!!!!!!! this is amazing work missy I bet MikuHoshi was very pleased to get such a Stunning gift hehee Anyways I love this Draw because There are TWO SONICS hehehe two cute hedgeies haha Also I love the color choices you made they give this a good feel to the drawing also Ilike how the younger sonic is on top with a strawberry cake its soo cute! haha This is just amazing art also heehee OF COURSE IT IS ORIGINAL hahaha im i dont think you want to give someone something that was copied hahaa. anyways I love This Artwork it Spectagular and very well drawn Im glad you made it hehee