Officer Frank is a cop in the 2003 TV series of TMNT and the Dreamwave comics. His design is based on TMNT co-creator, Kevin Eastman.
2003 Series
He and his partner Officer Laird first appear in the episode Things Change, and later in The Shredder Strikes Back, Part 2, The Return of Nano and The Christmas Aliens. He is voiced by Pete Capella.
Dreamwave
The first issue of Dreamwave Comics' brief run of TMNT comics, also titled Things Change, shows John and the police officer modeled after Kevin Eastman (here named 'Frank'), as childhood friends. They were present at the accident that lodged the four baby Turtles and ooze canister into the sewer.
The rest of the issue proceeds much like the episode version, although John and Frank catch sight of one another and lament the career choices one another has made.
At the issue's conclusion, following John's death, Frank spots the item John had dropped in the alley - a photo of the two of them as children.