A Time Portal is a form of portal used as a time machine. It appears in the 1987 cartoon episode Attack of Big MACC. Unlike many other portals, viewers are allowed to see through the portal to the other side.
MACC arrives through a time portal. When Krang reprograms him, he plans to use the Time Portal to bring an army of MACC's fellow robots into the Technodrome. However, Krang is defeated and MACC returns home through the portal.