From Muppet Wiki

A list of Muppet twins.

• Scooter and Skeeter (Muppet Babies)
• Kermit and Fozzie (The Great Muppet Caper only)
• Bert and Bart (Sesame Street)
• Betina and Belinda Cratchit (The Muppet Christmas Carol)
• Joey and Davey Monkey (Sesame Street)
• The Busby Twins (Sesame Street)
• Chip and Dip (Sesame Street)
• Andy and Randy Pig (Muppet Classic Theater)
• Pizza Twins (The Great Muppet Caper)
• The RX Twins (Pak-Nit Commercials)
• Wilbur and Orville Wright (The Muppet Show episode 518)
• The Invisible Twins (Statler and Waldorf: From the Balcony)