Executive Meddling: A couple times, when the judges believed an act made a bad song choice, the performers mention that producers influenced that decision (Arcadian Broad in Season 4 with a High School Musical number, the Fiddleheads doing "Billie Jean" in Season 6).
Alice Tan Ridley, At Last, and Sideswipe, among others, from the short-lived FOX series 30 Seconds to Fame.
Strikers All-Stars, Ring Masters, and Status Quo (as SQ Entertainment) from America's Best Dance Crew
Also works in the reverse with AGT acts appearing on other shows — most notably Jabbawockeez on America's Best Dance Crew. One of the guys from Sideswipe also later landed a starring role in Kamen Rider Dragon Knight.