Hints

Here I've listed (and will continue to list,when noticed of more) hints of this couple from various games and cartoons.

Games-

Sonic Heros-

When Team Rose fights Team Hero,if you play long enough and listen carefully,Knuckles shouts this to Sonic.

"Sonic,are you playing with that poor girl's heart again?"

Cartoons-

Sonic X-

Knuckles and Amy walk through the sewer in episode #3,through the begining,bickering and arguing. When the come out and see Sonic fight,Amy rushes in,and Knuckles looks generally worried about her,and goes after her.Amy is captured,and Knuckles attempts to save her,but Sonic wins that one...Knuckles seems a little jealous when Amy runs into Sonic's arms.

In Episode 5,near the end, Amy talks with Knuckles after he fights Sonic.He yells at her,but seems a little amused afterwards.

In Episode 10,the gang plays baseball,and look who sit together!

In Episdoe 36,they can't stop standing next to each other!

Updated Further Soon.