Caroll Spinney character transitions

Big Bird
Matt Vogel has served as Caroll Spinney's understudy for Big Bird, since the early 2000s. In most cases Vogel manipulates the puppet to Spinney's vocals (either pre-recorded, dubbed in post-production, or provided live on set), however there have been several appearances and performances where Vogel has provided the vocals for Big Bird as well, most notably in the Journey to Ernie segments that ran from 2002 to 2005.

Appearances where Matt Vogel performed Big Bird's voice:
 * Sesame Street
 * All Journey to Ernie segments
 * Episode 3816: Baby Bear's cousin Oliver returns (street scenes)
 * Episode 3833: Telly and the Mysterious X (street scenes)
 * Episode 3877: Elizabeth is visited by a Fairy Bubbleperson (street scenes)
 * Episode 3907: Runaway Ts (street scenes)
 * Episode 3972: Mumford makes the letter "S" disappear (street scenes)
 * Episode 4009 (speaking vocals only)
 * Episode 4028 (speaking vocals only)
 * Episode 4042 (speaking vocals only)
 * Episode 4074: Telly joins the Letter of the Month Club (street scenes)
 * Episode 4075: Cookie Monster writes a story (street scenes)
 * Episode 4107 & Episode 4108: The Adventures of Little Big Bird (as Little Big Bird only)
 * Episode 4155 (for Big Bird's brief appearance at the beginning of the street scene)
 * Episode 4503 (ending only)
 * A sketch where Big Bird explains to Elmo that plants can't play catch
 * A sketch where Big Bird watches Elmo show up and down
 * A segment where Big Bird and Snuffy present The Spanish Word of the Day: teléfono (telephone)
 * A segment with Laura Bush.
 * Waiting for Big
 * Elmo's World: Transportation
 * Elmo's World: Singing
 * Elmo's World: Exercise
 * Elmo's World: Skin
 * Elmo's World: Cameras
 * Elmo's World: Happy Holidays! (except for Big Bird and Snuffy's Christmas card)
 * The Street We Live On (intro to Journey to Ernie)
 * Elmo's Christmas Countdown (Speaking vocals for "I Want a Snuffleupagus for Christmas)
 * Elmo's Super Fun Hero Show
 * Once Upon a Sesame Street Christmas "The Twelve Days of Christmas" promo
 * Sesame Beginnings (as Baby Big Bird)
 * Beginning Together
 * Make Music Together
 * Exploring Together
 * Moving Together
 * The Furchester Hotel
 * Episode 201: A Big Bird Surprise
 * Episode 216: A Furchester Christmas
 * Guest Appearances
 * "Jerry Nelson: A 65th Birthday Celebration" (1999, Big Bird's first three lines only)
 * Emmy Awards (2003)
 * The Today Show (December 2005, November 2015, January 2017, February 2017)
 * The Early Show (October 2011)
 * Good Morning America (September 2013, January 2016)
 * Christmas with the Mormon Tabernacle Choir (December 2014)
 * YouTube Rewind: 2014 (December 2014)
 * The Colbert Report finale (December 2014)
 * Billy on the Street (February 2015)
 * "Big Bird Interns at Funny or Die" (November 2015)
 * Super Bowl 50 opening video (February 2016)
 * CBeebies Bedtime Stories (November 2016)

Oscar the Grouch
By 2015, Eric Jacobson became Spinney's understudy for Oscar the Grouch; often lip-syncing to a prerecorded vocal track by Spinney, and other times doing the voice himself.

Appearances where Eric Jacobson performed Oscar's voice:
 * Sesame Street
 * Once Upon a Sesame Street Christmas "The Twelve Days of Christmas" promo
 * Guest Appearances
 * Sunny Side Up (February 2015)
 * Last Week Tonight with John Oliver (April 2016)
 * Sesame Studios YouTube Promo (May 2016)
 * Today (January 2017, February 2017)
 * Ellen (January 2017)
 * "Sesame Street Spreads Kindness at Fast Company" (January 2017)