A few things to consider...
1 Splurge, couldn't ell you if there were clowns or not in that number animation sequence due to my blind batty eyes.
2 To my knowledge, this is the first time that Snuffy has been fully invisible. During the earlier seasons until 1986/1987 Snuffy was thought to be imaginary and not invisible. He appeared in all his visible physique when playing with Big Bird, but cause of his initial shyness to anyone else he'd quickly depart before other people came. That's why everyone thought Snuffy to be imaginary.
My Thoughts on 4070.
Pros.
1 Story segment was OK. Notice how quickly they ditched Elmo from the beginning of the episode?
2 Did you catch the lyrics of the song between Big Bird and Snuffy? At one point BB mentions Snuffy's derriaire.
3 Song by Cookie Monster: "What Friend For?" Was this the original airing with a non-named purple boy monster alongside CM?
4 Letter of Day: O was new. Cookie keeps eating the letters thinking they're cookies.
4 Soul O song/cartoon.
5 Hip-Hop performance of an O song.
6 Bert and Ernie sketch with Frank's Bert voice, Ernie uses the fan to blow Bert's book about air out the window before they end up playing baseball.
7 Global Grover's second visit to Australia ends up with Grover the rescuer being rescued by the animals he wants to rescue.
8 Celebrity Moment: Finally know who Celia Cruz is and I remember two songs she did; one about the hummingbird or zum-zum, and another with AM's holding up poles with the numbers 1 to 10.
Though the celebrity misspoke, the Spanish word for a memory that you cherish or remember is "recuerdo"; "memoria" is the Spanish word for the retentive power of memory itself.
Cons.
Number 14 segment was reused.
2 Didn't particularly like the Erika Vadu song.
Also, Elmo's World was new and the jokes with Ernie and Officer Duckie were OK.
Hope this helps and have a good day.