Sonic & SEGA All-Stars Racing

Start a quick race as sonic (track dosent matter) of about 3 or 4 laps.
If eggman is not there quit to the main menu and try again.
When he appears fall to 8th place and drive into the mystery boxes until you get a picture of some jewels. Drive a short distace behind Dr Eggy and use the all star move. When directly behind him mash the A button. If you hit him the Achievement will pop.
Congrats on you 15g!
Happy achievement hunting!

you can also get this acheivement using 2 controllers,set your race to 2 or 3 laps,preferably whale lagoon,if u r player one who wants this acheivement,have player 2 select eggman,and hit him with an sonics all star move if u are able to acquire through the roulette with the ? block,just have him stay at the finish line when the race starts and hit him with it,worked for me cuz it appeared in the acheivements list 4 me!(Sonic Unleashed)

Do a quick race as sonic on any track of 9 laps. Try and start the race in 8th place so that you have more chance of getting the all star boost earlier in the race and it gives you a second chance to get the all star boost if you miss on your first attempt. When you get behind eggman do as DarthPootie says. I suggest 9 laps as it gives more milage towards the licence achievements if you haven't already got them